64 BASTERIA, Vol. 1, No. 4, 1936

of steinii Remarks on the generic position Hydrobia

E.A. Smith von Martens and Paludestrina taylori

with the description of a new

by Amsterdam. C.O. van Regteren+Altena Zoological Laboratory,

of this Mr. P r i n s drew attention to In April year J. my

the of Vreeland a locality in neighbourhood (prov. Utrecht)

in I availed where Hydrobia steinii occurs great quantities. myself of this opportunity to study this little snail more closely.

authors about the The different do not agree systematic position of this within the family Hydrobiidae. At

the view that it is C 1 e s s i n present prevails no Hydrobia. another was the first to place the present species in genus,

it in in his "Deutsche Excursions-Mollusken-Fauna" we find the 4 x Several authors have fol- genus ( ), p. 326).

1 i in steinii as lowed C e s s n regarding Hydrobia belonging

K who had studied the to Bythinella and recently r u 11,

arrived the conclusion that anatomy of Hydrobia steinii, at it is really a true Bythinella (11, p. 462, nr. 15).

On the other hand Jackson & Taylor (#) have poin-

which between ted out the great resemblance exists Hydrobia steinii and Paludestrina taylori E. A. Smith. The latter

Hydrobiid, which lives in England, is considered at present

— — mainly on account of the shape of its egg-capsules to

the American Amhicola. The shells of these belong to genus

resemble each that E. A. Smith two species so closely other, himself thought it impossible to distinguish them, but he

the preferred to keep the two forms separated until of both had been studied more closely. In the opinion of E.

Paludestrina differed von Martens, however, taylori

form from his Hydrobia steinii by its more conical broader

The resemblance between the forms (8, p. 9). striking two has induced Ehrmann to class steinii (3, p. 198) Hydrobia in the . genus

first do for to A thing to me consequently was compare

from Vreeland with Paludestrina In my specimens taylori.

71. *) The numbers refer to the list of literature on p. C. O. van R. Altena: Hydrobia steinii Mart. 65

the data in the literature I had at addition to my disposal a

animals — series of specimens — shells containing dried up

R. 1 B. T 1 i from Dukinfield, Cheshire, J. e o m n leg., pre-

served in the Zoological Museum at Amsterdam. From one

of these could the and the specimens I prepare penis radula,

which to be identical with the proved corresponding organs

in Hydrobia steinii.

Moreover I could watch the living of Hydrobia

which in detail with the steinii, appeared to correspond every

Smith description of Paludestrina taylori given by (14, p.

I observed the characteristic above 192). even sulphur spot

each which Smith draws attention. eye, to special Speci-

Vreeland 30th 1936 de- mens collected by me at on April

posited their egg-capsules in the first or second week of May;

these egg-capsules (fig. 1) are quite similar to those described

and figured by Jackson & Taylor (8, p. 10, fig. 3—5) from Paludestrina taylori.

looked in vain for difference in the shells of the two I any

forms, it certainly cannot be found in the relation length:

when the of breadth as is evident comparing measurements a

series of each form:

A. Paludestrina taylori E. A. Smith, Dukinfield, J. R.

le B. Tomlin leg.

Number of specimens 1 2 1 2 3 2 i 2 1

Length ') 2,9 2,8 2,7 2,7 2,6 2,3 2,2 2,1 2,0

Breadth *) 1,9 1,8 1,7 1,6 1,7 ;i,5 1,5 1,5 1,6

B. Hydrobia steinii von Martens, Houten (prov.

Utrecht), M. M. Schepman leg., in collection Zoological

Museum, Amsterdam.

Number of specimens 1 2 2 3 1 1 1 1 2 1

Length *) 2,6 2,5 2,5 2,4 2,4 2,4 2,3 2,2 2,1 2,0

Breadth ') 1,6 1,7 1,6 1,6 1,5 1,4 1,5 1,5 1,5 1,4

*) In mm. 66 BASTERIA, Vol. 1, No. 4, 1936

This last set apparently belongs to the forma scholtzi A.

Schmidt, which occurs locally and remains smaller than the

typical Hydrobia steinii. From other Dutch localities the

Zoological Museum possesses larger specimens e.g.:

C. Rhoon (prov. Zuid Holland), M. M. Schepman leg

Number of specimens 1 1 . . .

Length *) 2,8 2,8

Breadth') 1,8 1,7

D. Utrecht, C. Druyvesteyn leg.

Number of specimens 1

Length . 3,1 v

Breadth *) 1,9

to detect difference in between Failing any any organ Hy-

drobia steinii and Paludestrina taylori I am led to the con-

clusion that the latter is with the former. synonymous

I have nothing to add to the description of the animal, the

S K shell and the operculum as given by m i t h (14). r u 11 (11,

the formula for the different teeth p. 413) gives following

of the radula:

(4~ 5) + 1 + (4-5) Central.Central • (J _2)

Lateral: 2 —3 + 1+3.

Inner marginal: 20—22.

Outer marginal: ca. 30.

observations the results: My own gave following

4 + 1 + 4 Central: 2 2

Lateral: 2 —3 + 1 + 3—4.

Inner marginal: + 20.

Outer marginal: X.

*) In mm. Altena: steinii C. O. van R. Hydrobia Mart. 67

11 has not the radula and h K r u figured J o a n s e n (9, p.

423, fig. 10) only figures the central tooth, so it might not be

superfluous to figure the radula of Hydrobia steinii here

(fig- 2),

The bears truncated which is verge a flagellum sheath,

much shorter than the penis and which is only partially con-

nected with it at the base (fig. 3a). The penis is of a greyish

hue, the flagellum sheath is white.

Now the which we may turn to question to genus Hydrobia

steinii belongs.

of The true Hydrobiae (Paludestrinae) are inhabitants brackish their lack the sheaths and waters, penes flagellum

their shells with It is evident that are provided acute tops.

steinii does not to this Moreover Hydrobia belong genus.

Krull {11) has pointed out several anatomical differences between the side and ulvae Hydrobia steinii on one H.

(Pen n.) and H. stagnalis (B a s t.) on the other.

The radula of steinii resembles the Hydrobia very closely ra-

dula of Bythinella, but the latter is distinguished by one basal

denticle on each side of the central tooth. This little difference

in the radulae might not be a sufficient reason to remove Hy-

drobia from the there other steinii genus Bythinella, but are

more serious objections to such a view.

All true Bythinellac are stenothermal inhabitants of cold

waters, they are to be found in wells etc. Bythinella dunkeri

f 1 has of about (v. F r a u e n e d) an optimum-temperature

10° C. and its in These deposits eggs February (3, p. 277).

are as in but the eggs deposited single, Hydrobia steinii, egg-

have the of small capsules shape a watchglass (3, p. 268; pi. J 6,

The main difference is the of the fig. 13). given by shape verge.

This of furnished consists a penis with a flagellum sheath,

which is as long as the penis and is its backward prolonga-

tion. At the end the flagellum sheath is swollen and flattened.

The of the of is thus described and shape verge Bythinella

from figured by B r e g e n z e r (3, p. 265, fig. T) B. dunkeri and I can affirm his statements after examination of a male

specimen of B. brevis (Draparnaud) (fig. 3b). 68 BASTERIA, Vol. 1, No. 4, 1936

the of the and the of Thus the , shape verge shape

the egg-capsules of Hydrobia steinii and the species of the

do and besides K 11 has detected genus Bythinella not agree, r u

in be- differences the nervous system and the female genitalia

steinii dunkeri 428 & tween Hydrobia and Bythinella (11, p.

think conclude that steinii does p. 444). I we may Hydrobia

the not belong to genus Bythinella.

The shell of Hydrobia steinii resembles the shell of some

classified in the Amnicola and Hydrobiids genus placed by

his in F. C. Baker in new subgenus Marstonia 1925.

Thiele has removed the Marstonia {15, p. 376) subgenus

the but to C. k to genus Lyogorus, according F. Ba e r (1, p.

the and the in Marstonia si- 106 seq.) verge egg-capsules are and therefore reasonable milar to those in Amnicola, it seems

of Amnicola. to me to maintain Marstonia as a subgenus

of the radula of steinii The general aspect Hydrobia re- examined sembles that of Marstonia, but when the two are in

detail it that differ in several from each appears they respects

has shorter other. So the radula of Hydrobia steinii cusps on

the different teeth, it has two instead of one basal denticle on

the central tooth and the shape of the lateral and marginal

teeth is somewhat different from the shape of those in Mar-

freshwater — canals stonia. In being an inhabitant of lakes,

with but the etc. — Hydrobia steinii agrees Marstonia, verge

the of the do For the fla- and shape egg-capsules not agree.

Baker gellum sheath — judging from the figure by F. C.

with the — has base (1, p. 95, fig. 43) a common penis of (fig. 3c), whilst the egg-capsules Marstonia (/, p. 129, fig.

those of but lack 56B) have a keel just as Hydrobia steinii,

the basal ring, which is conspicuous in the egg-capsules of the

latter species.

Accordingly it seems impossible to classify Hydrobia steinii

in of the or Amnicola one genera Hydrobia, Bythinella (Mar-

have been able find other stonia) and I not to any genus to

which it could be transferred. Therefore I the propose new

for that genus Marstoniopsis Hydrobia steinii, being aware Altena: steinii Mart. 69 C. O. van R. Hydrobia

further systematic investigations in the family Hydrobiidae

be of some might prove it to a subgenus or a genus detail already established, but not examined in up to now.

difficult of the It is to give a diagnosis genus Marstoniopsis

there — the as is only one species genotype Marstoniopsis

but the steinii (von Martens) — known to belong to it, of this the main characters species may serve to construct

provisional diagnosis which follows:

Shell: whorls subcylindrical, turreted, umbilicated; very convex separated by a deep suture; peristome continuous, outer

margin simple.

Operculum: paucispiral, thin, horny, slightly concave ex-

teriorly.

Animal: tentacles moderately long, scarcely tapering, eyes

at the outer base of the tentacles with a sulphur-coloured spot above each.

Radula: resembling that of Bythinella, but central tooth

with two basal denticles on each side.

Verge: provided with a flagellum sheath, which is only par-

with the base. tially connected it at

Egg-capsules: single, provided with a keel and a basal ring.

Habitat: fresh water.

Distribution: northwestern Europe.

The distributional area of Marstoniopsis steinii comprises

the continent to E h on (chiefly according r m a n n, 5, p. 198):

the Netherlands (prov. Noord Holland, Zuid Holland, Utrecht and Overijssel), nearly the whole of Germany excepted the

in Latvia southwestern part, some localities Poland, and near

of localities Riga, the southwestern part Finland, two in Russia

& and scattered localities (lake Ladoga gouvernement Twer)

in Denmark and the south of Sweden.

In England Marstoniopsis steinii is reported from: „in ca- nals Manchester and other in Lancashire and near places

Cheshire" This isolated the (6, p. 81). area suggests possibility that the species has been introduced into England from else- where. Smith Ellis and So E. A. (14, p. 191), (6, p. 81) 70 BASTERIA, Vol. 1, No. 4, 1936

deal with introduction of Boettger (2, p. 271) a possible

Marstoniopsis steinii from Tasmania or North America. Now

that it has been that proved Paludestrina taylori is the same

the first species as Hydrobia steinii one might presume in place that the species was introduced from-the continent of Europe.

It is curious that the oldest fossil specimens of Marstoniopsis

steinii known are recorded from England, i.e. from the pleist-

Cromer forest bed i d's of ocene (13, p. 198). R e figure one

of these specimens (12, pi. V, fig. 8) is inadequate for deter-

mination, but the remark of Sandberger (I.e.): "welche

Hr. C 1 e s s i n und ich von Originalexemplare der lebenden

nicht unterscheiden makes Form zu vermogen", it pretty sure

that it is really Marstoniopsis steinii that has been found in the Cromer forest bed. As far as I know on the continent

fossil specimens are only recorded from holocene deposits in

the of and neighbourhood Kalundborg (10, p. 8 & 10) near

Rostock (7, p. 167).

I indebted doctor E. W. I am greatly to professor J. h 1 e, director of the Zoological Laboratory, Amsterdam, for his kindness in me to on in his allowing carry my investigations laboratory and to professor doctor L. F. de Beaufort, director of the Zoological Museum, Amsterdam, for the loan of specimens.

Summary

Paludestrina E. A. Smith is of 1. taylori a synonym Hy-

drobia steinii von Martens.

neither 2. Hydrobia steinii is no Hydrobia, nor a Bythinella,

an Amnicola (Marstonia); on account of the resemblance

to the of this species subgenus a new genus Marstoniopsis

has been established for it.

3. Marstoniopsis steinii, which has been recorded from the

pleistocene of England (Cromer forest bed) has probably

its in died out since in that country; actual occurrence

the environment of Manchester be due reintro- may to

duction from in the northwestern of the its area part

European continent in historical time. C. O. van R. Altena: Hydrobia steinii Mart. 71

Literature cited.

1. Baker, F. C., 1928, The freshwater of

Wisconsin, Part I , Bull. Wis. Geol. N. H.

vol. Survey, 701, 507 pp., 28 pis.

2. Boettger, Caesar R., 1931, Artanderung unter dem

Archivo Zool. vol. Einflusz des Menschen, Ital., 16, p.

250—283.

3. Bregenzer, Aloys, 1916, Anatomie und Histologic

iiber von Bythinella dunkeri, nebst einem Anhang vier

neue Cercarien aus derselben, Zool. Jahrb., Abt. f. Anat.

d. Bd. Taf. u. Ontog. Tiere, 39, p. 237—292, 31 Fig., 16.

C i Deutsche Excursions-Mollusken- 4. 1 e s s n, S., 1876,

Fauna, Niirnberg.

5. Ehrmann, P., 1933, Mollusken (Weichtiere), in:

Brohmer, Ehrmann & Ulmer, Die Tierwelt Mitteleuropas,

2. Bd., 1. Lief., Leipzig.

6. E 11 i s, A. E., 1926, British Snails, Oxford.

G Unsere Land- und Siiszwassermollus- 7. e y e r, D., 1927,

ken, 3. Aufl., Stuttgart.

k T 1 Observations 8. J a c s o n, J. W. & a y o r, F., 1904,

of on the habits and reproduction Paludestrina taylori,

of vol. Journ. Conch., 11, p. 9—11, 5 fig.

9. h a e A. i Randers J o n s n, C., 1918, Bloddyrene Fjord,

in: Randers Fjords Naturhistorie, p. 393—444, 19 fig.,

Kopenhagen.

h A. C. & L Om Land- 10. J o a n s e n, y n g e, H., 1917,

Ferskvandsmolluskerne i holocaene ved Strand- og Lag

SSO for deres gaarden, Kalundborg, og Vidnesbyrd om

Klimaforandringer, Medd. Dansk geol. For., Bd. 5, nr. 11,

krt. 19 pp., 9 fig., 1

11. Krull, Herbert, 1935, Anatomische Untersuchungen

einheimischen Prosobranchiern und an Beitrage zur Phy-

logenie der Gastropoden, Zool. Jahrb., Abt. f. Anat. u.

d. Bd. Ontog. Tiere, 60, p. 399—464, 22 Fig.

R Pliocene of Mem. 12. e i d, C., 1890, deposits Britain, Geol.

Survey Un. Kingdom, London. 72 BASTERIA, Vol. 1, No. 4, 1936

d b Ein Kenntnis der 13. S a n e r g e r, F., 1880, Beitrag zur

unterpleistocanen Schichten Englands, Palaeontographica,

Bd. Taf. 27, p. 83—104, 12.

14. S E Notice of of m i t h, d g a r A., 1901, a Species Pa-

ludestrina new to the British Fauna, Ann. & Mag. N. H.,

series vol. 7, 7, p. 191 —192.

T h i 1 Revision des der 15. e e, J o h., 1928, Systems Hydro-

biiden und Melaniiden, Zool. Jahrb., Abt. f. System.,

d. Bd. Oekol. u. Geogr. Tiere, 55, p. 351—402, 63 Fig.,

Taf. 8.

Samenvatting

Dit voorjaar stelde de heer J. Prins mij, door mij een rijke

vindplaats van Hydrobia steinii von Martens in de om-

in slak geving van Vreeland aan te wijzen, staat om deze

nauwkeurig te bestudeeren.

Een vergelijking met de beschrijving van Paludestrina tay-

lori E. A. Smith en met exemplaren van die soort uit de

Museum collectie van het Zoologisch te Amsterdam bracht

het dat deze beide zooals reeds aan licht, vormen, trouwens

door andere auteurs was verondersteld, identiek zijn. Daar de

naam Paludestrina taylori jonger is dan Hydrobia steinii, moet

hij vervallen.

In de literatuur heerscht over de geen eenstemmigheid vraag

tot welk geslacht Hydrobia steinii gerekend moet worden. Het

onderzoek van de verschillende voor de systematiek belang-

als: radula den rijke organen schelp, en penis, van vorm van

hoewel de eierkapsels en van de levenswijze wees uit, dat, er

zeker het het verwantschap met genus Bythinella en subgenus

Marstonia van Amnicola bestaat, de soort niet tot een van

deze evenmin als worden. genera, tot Hydrobia gerekend mag

familie Een ander geslacht uit de Hydrobiidae, dat in aan-

komt werd merking om Hydrobia steinii op te nemen, vergeefs

Daarom gezocht. leek het raadzaam voor Hydrobia steinii een nieuw te de genus op stellen, waaraan naam Marstoniopsis

werd gegeven.

De oudste fossiele exemplaren van Marstoniopsis steinii zijn Altena: steinii C. O. van R. Hydrobia Mart. 73

gevonden in het plistoceene Cromer forest bed in Engeland.

komt de dat land verschillende Tegenwoordig soort in voor op

plaatsen in Lancashire en Cheshire in de omgeving van Man-

Dit chester, waar zij in 1900 voor het eerst werd aangetroffen. beperkte gebied van voorkomen en de betrekkelijk jonge

datum van de eerste vondst van deze soort in Engeland doen

dat steinii of veronderstellen, Marstoniopsis nog tijdens na het plistoceen in Engeland is uitgestorven, doch in historischen tijd

het noordwesten het vasteland van van van Europa, waar zij

in is op talrijke plaatsen voorkomt, uit, weer Engeland ge- importeerd.

Fig. 1. Egg-capsules of Hydrobia steinii von Martens (longest diameter about 1 mm.), original.

Fig. 2. Teeth of the radula of Hydrobia steinii von Martens,original.

3. Sketches to show the and the situs of the in: Fig. shape verge

a. Hydrobia steinii von Martens, b. Bythinella brevis (Draparnaud), Amnicola limosa c. porata (Say); a & b original, c. after F. C. Baker.