458 Bibliographical Notices. 



succeeds an historical introduction and observations on the generic 

 characters, with a classification of the species. A detailed descrip- 

 tion of each sjjecies is given, to which is appended a very complete 

 synonymy. From the geologic and geographic distribution which 

 follows we extract a few notes. The number of species of Productus 

 described amounts to 62, of which 4 are Devonian, 47 Carboniferous, 

 10 Permian, and 1 Triassic. Of the 47 Carboniferous species 35 only 

 are found in the lower divisions, viz. : — 



P. striatus. P. proboscideus. P. coatatus. P. fimbriatus. 



— ffiganteus. — genuinus. — subquadratus. — Buchianus. 



— latissimus. — Nystianus. — brachytbserus. — Desbayesianus. 



— flexistria — Medusa. — spinulosus. — marginalis. 



— mammatus. — plicatilis. — Villiersi. — granulosus. 



— arcuaiius. — Gviffithianus. — tessellatus. — Orbignianus. 



— porrectus. — subla'vis. — Humboldtii. — Vevneuilianus. 



— undatus. — Boliviensis. — pyxidiformis. — Christiani. 



— expansus. — Leuchteiibergensis. 



Not any species belongs exclusively to the middle division, al- 

 though 7 are common to the lower and middle portions, viz. P. mar- 

 garitaceus, undiferus, Flemingii, pustulosus, Keyserlingianus, aculeatus, 

 mesolobus. The P. carbonarius is found only in the upper division. 

 The P. Cora, semireticulatus , scabriculus and punctatus appear to 

 have lived from the commencement to the close of the carboniferous 

 period. 



It is interesting to observe that all the Devonian species have 

 common general characters, and may be arranged in the same group 

 (Caperati) ; a similar remark also applies to the Permian species, 

 which, with the exception of three, are nearly all comprised in the 

 group (Horridi), so that the latter group is almost composed of Per- 

 mian species, the P. Orbignianus, P. Verneuilianus , being the only 

 carboniferous forms ; and it is not a little singular, in consulting 

 the table of classification (page 29), to find that the Permian species 

 have a much greater affinity with the Devonian than with the car- 

 boniferous, notwithstanding the considerable period which must have 

 elapsed between their development. 



Under the geologic distribution of the genus Chonetes we find there 

 are 23 species known at present, which number may probably be in- 

 creased when the fossiliferous deposits of America, New Holland and 

 Asia are more explored. Nevertheless the geological results to which 

 the known species lead us are deserving of notice. From the obser- 

 vations of M. de Koninck it appears (contrary to the opinion gene- 

 rally admitted), that with the exception of one, not any of the 23 

 species pass from one system to another, or even from the lower to 

 the upper beds of the same system. 



The following table shows their distribution in the different parts 

 of the palaeozoic series : — 



