486 Reviews—Barrande's Silurian Cephaloppda. BBVIE"WS. DISTRIBUTION OF THE CEPHALOPODA IN SILUBIAN COUNTRIES. By JOACHIM BARRANDE. (Extrait du Syst. Silur. du Centre de la Boh^me. Vol. II. 4me serie, pi. 351-460.) Prague, 1870. 8vo. pp. 480. TTTE hare already directed the attention of our readers to M. T V Barrande's great work on the Cephalopoda of Bohemia. (See GEOL. MAG. 1866, Vol. HI., p. 32, and 1867, Vol. IV, p. 322.) In the present volume M. Barrande has prepared, with the most laborious care, a summary of the whole of the vast array of facts and details relating to the geographical and geological range of the Cephalopoda in Silurian countries, and presents us with his de- ductions therefrom. M. Barrande excuses himself for the space which he has occupied in the consideration of the Cephalopoda, by showing how vast was their geographical range in Silurian times, and also because they re- presented (if we except the scanty remains of fishes in the older palaeozoic rocks) almost the highest class of living organisms. In the earlier Silurian stages (Fauna II. of Barrande), the Cephalopoda were certainly the dominant class, and it was only towards the close of that great series of deposits that their reign was disputed by the earliest Fishes and the great larval-like Crustaceans of the genera Pterygotus and JSu/rypterus. Upon the question of the comparative strength of the two classes, the Mollusca and Crustacea, when tested by the relative fecundity of the two groups, M. Barrande seems disposed to divide the palm between the Cephalopoda and the Trilobita, which appear to have been equally innumerable. But in organization and in relative age, the Trilobita are pre- eminent. For in the Primordial zone (Fauna I. of Barrande), they represent nearly the entire fauna, whilst not a trace of the Cephalo- poda has as yet been met with in these earliest stratified rocks. In the Upper Silurian stages, the abundance of the Cephalopoda would lead one to expect that they would have been discovered in the Primordial rocks, but such is not the case at present, and it would appear that the Trilobita were really called into existence ages before the Cephalopoda. It is but reasonable, however, to assume that a great break in time exists between the Primordial Silurian and the Tremadoc rocks in which the Cephalopoda first appeared. When the relative numbers of the.two great groups are compared, the difference is but very small, thus:— Total number of Trilobita, 1677 ( *ff*& *» Primer- ( dial zone. s cond Total number of Cephalopodar v ,> 162 2 (^ ^f™thir d *?Siluria, ? n stagest "^. Difference, 55 Heviews—Barrande's Silurian Cephalopoda. 487 So that, assuming there may be 55 species of Trilobites found in the Primordial zone in the rest of the Silurian, series, the hosts of the Cephalopoda equal those of the Trilobita. In the first appearance of the Cephalopoda, it is interesting to notice that they are met with not only in widely separated geogra- phieal positions, but also in great generic and specific variety. The total number of types in this class is 25, and of these 12 make their appearance in the earliest stage of their incoming. (See the following table.) The subjoined Diagram represents the extension of the principal generic types of the order of the Cephalopoda which appeared during the Silurian period.1 PAL2EOZOIC. SILURIAN FAUNAS. MESOZOIC. II. III. TRINCIPAL or COSMOPOLI TAN TYPES. i Omiatiies O Phragmectra* Oomphtttrat. TncHoitrat... JEnioeeftu ... ZUuitei.. , NatUiltu Cyrtoetrat ... Orthaetnu ... Of tire Secondary or local types one, Bactrites, ranges from the Silurian (H.) to the Devonian. Five, Pibeeras, Bathmocerae, Cono- ceras, Gdmoeerat, Disooceras, occur only in the lower stages of Fauna (H). Ophidoceras occurs in the Llandeilo and Wenlock stages. TretoetrM occurs in the Llandovery and in the Ludlow stages. Three, Euronla, Aphragmites, and Glossoceras, occur only in the Wenlock and May Hill stage, the lowest part of Fauna (HI.); lastly, three, JSereo- ceras, Nothoteras, and Adelphoceras, occur only in the Uppermost Silurian of Fauna (HL) In another table (too large to be reproduced here), M. Barrande shows the first appearance of the types, and he observes that in each principal region compared, there is a very great diversity both in the first generic appearance, and also in the numbers met with. Thus in Canada a small Orthoceras first appears at the base of the Calciferous sandstones; in England a small Cyrtoceras is found in the Tremadoo slates; in Bussia eight different types are met with in the Orthoceras limestone; whilst in Bohemia seven types appear together in Bande d 1 of M. Barrande (or Tremadoc ?). M. Barrande divides the Cephalopoda into three families, the Goniatidce, the Nautilida, and the Ascoceratidm. The first of these 1 Taken from Barrande's work (p. 266). 488 Reviews—Barrande's Silurian Cephalopoda. includes the genera Ooniatites and Bactrites, the last Ascoceras, Aphragmites and Glossoeeras, Barr., whilst the NautiliAm includes twelve genera, embracing all the varieties of form of shell, from the straight Orthoeeras to the perfectly coiled Nautilus and Troehoceras. The number of species derived from the twelve types of Nautilidm is 165, representing about one-third of the 478 forms which charac- terize Fauna II. in all the Silurian countries. Thus at the outset of this group we find it largely represented both in genera and species. About three-fourths of the 165 species mentioned above are found by M. Barrande to be extremely local; this would seem to contradict the idea of the free pelagic habits of these mollusca; there may have been, however, other impediments; for the world-wide homogeneous conditions of climate in Silurian times, is, after all, only an assumption, whilst land barriers may have opposed the migration of marine faunas, even more effectually than they do at the present day. The following Table cannot fail to interest English palaeontologists, giving aa it does a summary of the British Cephalopoda. SILURIAN FAUNAS. I. II. III. ENGLAND, SCOTLAND, •a . AND IKELAND. 11 Number of types in each stage. Cyrloeeras, Golf, 4 sub. gen. Piloceras, Salt. Orthoeeras, Breyn. 23 15 19 25 sub.gen. Endoceras, Hall. Zituites, Breyn. i? Gomphoceras, Sowby. Tretoceras, Salter. 1 Phragmoeeras, Brod. 3 Troehoceras, B.H. 1 10 Ascoceras, Barr. 1 Appearance by stages. 1 10 37 21 25 30 124 32 92 Total appearances for each >— Fauna 69 55 Reappearances between different stages to be deducted 9 12 60 43 103 Eeappearances between the II, and III. Faunas to be deducted 11 Total number of distinct British species... 92 Reviews—Barrande's Silurian Cephalopoda. 489 We should take care to mention, here that M. Barrande divides his geographical distribution of the Cephalopoda into three parts:— A. GRAND CENTRAL ZONK OF EUROPE, which includes Bohemia, France, Spain, Portugal, and Sardinia. B. GRAND NORTHERN ZONE, subdivided into I. EUROPE, Great Britain, Norway, Sweden, Eussia, Thuringia, Franconia, Saxony, Germany, and Holland. II. NORTH AMERICA, Newfoundland, Acadia, Canada, New Brunswick, New Tork, Wisconsin and Illinois, Missouri and Tennessee. C. DIVERS COUNTRIES, consisting of the Himalayas and Tasmania. After investigating the principal phenomena presented by the successive evolution of the Cephalopoda in the vertical series of the Silurian deposits, M. Barrande has endeavoured to ascertain how far that chronological evolution accorded with the zoological develop- ment of the group, and he then proceeds to draw a parallel between the two. This concordance, M. Barrande observes, would be at once evident if the most simple forms appeared first, and the most complex last, in the series of Silurian rocks. The author maintains, however, that such is not the case. Thus the most simple forms, the Ascoceratides, do not appear until the close of the second fauna in Canada, and at the commencement of the third fauna in Bohemia; whilst forms the most complex, such as Nautilus and Trochoceras, appear at the beginning of the second fauna in America, so that it would seem there was an interval of nearly the length of the entire series of deposits forming the second fauna of Barrande, before the appearance of the simple forms, during the whole of which period the more complex forms had existed. These facts the author considers are sufficient to show that there is an irreconcilable discordance between the chronologic and zoologic evolutions. M. Barrande considers that the total absence of Cephalopods in the Primordial Silurian strata does not permit us to suppose that the earlier types were developed during the existence of a hypothetical series of Anteprimordial faunas of which not a trace remains. In replying to M. Barrande upon this point it is needful to be most > cautious, for this reason, that he has gone so carefully into this grand question that it is hardly possible to find a flaw in the conclusiveness of his reasoning. We would, however, venture to suggest a few points deserving his attention. And first as regards the regions explored. M. Barrande has probably achieved more, single-handed, in the country of Bohemia, for the exploration and investigation of its fossil fauna, than has been done by the united labours of many men for any other country in the world. The result speaks most eloquently from the pages of M. Barrande's great work. In the Cephalopoda which we are now considering, we find the number of genera and species enumerated from Bohemia alone to exceed that of any other region in the world hitherto explored. 490 Reviews—Barrande's Silurian Cephalopoda. The following list will express the relative numbers described from the various geographical regions enumerated in the work before us:—^ Number Number GEOGRAPHICAL AREAS OF THE SILURIAN nf CEPHALOPODA.