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 genus
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 species 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 Bythinella ( ), 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 animals 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 Amnicola. 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 animal 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 ecology, 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 synonym 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 Mollusca of
Wisconsin, Part I Gastropoda, 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.