352 Bibliographical Notices. 



tylusy to which he refers the reader for this purpose, heing anything 

 rather than conclusive. 



We have already remarked, that the primary groups formed by the 

 author amongst the Gasteropodous MoUusca are identical in their 

 signification with those of De Blainville. This identity also prevails 

 to so great an extent in the contents of these divisions, that we are 

 involuntarily led to believe that Mr. Clark's system is really founded 

 upon that of the French author. Thus, his Hermaphrodita sine con- 

 gressu are the same as the Hermaphrodita of De Blainville, with the 

 mere addition of the Chitonidce, a group which De Blainville placed 

 amongst his Malentozoaria with the Cirrhopoda, considering them to 

 form a connecting link with the Articulated type of animals ; and this 

 agreement between the two authors is the more remarkable, as it 

 appears exceedingly doubtful whether the phsenomenon, from the 

 supposed occurrence of which this group is separated from the other 

 Gasteropoda, ever takes place in this class of animals. 



The other two groups, the Monoecious and Dioecious MoUusca, 

 exhibit a similar resemblance to the corresponding divisions in 

 De Blainville' s classification, the only difference being that Mr. Clark 

 transfers the Trochidce (with Valvata) and Vermetidce (including 

 Turrit ella) to the Hermaphrodite section. The grounds urged by 

 Mr. Clark in favour of this change, which is in direct opposition to 

 the views which have prevailed ever since malacology was first 

 studied, are by no means satisfactory, and he himself is forced to 

 admit that they are mere conjectures, — an admission which, it ap- 

 pears to us, must greatly detract from any value which might other- 

 wise attach to this system. In both these groups, his opinion that 

 the animals are monoecious, with congression, is founded upon the 

 circumstance that he has been unable to discover the male organs, 

 — certainly rather a curious proof of hermaphroditism*. Another 

 result of this adherence to an artificial system is, that the Pulmo- 

 niferous Gasteropoda occur in two of the primary divisions, — the 

 Helicidce and their inoperculated allies being placed amongst the 

 Hermaphrodita congressu, and the Cyclostomatidcc amongst the bi- 

 sexual (unisexual) species, under the denomination of Gasteropoda 

 Pectinibranchiata. Under all these circumstances, we have little 

 expectation that the sexual system as put forward by Mr. Clark will 

 ever find much favour in the eyes of malacologists, — and we must 

 regret that an observer of his reputation should have lent the sanc- 

 tion of his name to an arrangement so untenable. 



It is not, however, upon its systematic arrangement that the value 

 of the present contribution to malacological knowledge must depend, 

 although the author appears to attach no small importance to it ; the 

 work is chiefly interesting from its containing original observations 

 upon the structure and habits of a very great proportion of the Tes- 

 taceous MoUusca inhabiting the seas which surround these Islands. 

 We may remark in passing, that the work can scarcely be regarded 



* Other authors who have particularly examined the animal of Valvata, 

 referred by Mr. Clark to the Trochidce, have proved it to be undoubtedly 

 dioecious ; and Turritella is in the same case. 



