258 Lamarck's Genera of Shells. 



casteaux, commanded the expedition sent in search of La Peyrouse. 

 It is distinguished from the argonauta, by the spiral summit not 

 entering into the aperture, and by its having a single, sharp, in- 

 dented keel, the whole length of the back. The animal, moreover, 

 never conceals itself in the shell, which, probably, serves only to 

 protect the heart and branchiae, which are enclosed within it. 



Lamarck gives two other species, viz.,C. fragilis, from the Afri- 

 can Seas, and C. cymbium, (argonauta cymbium. Linn.) from the 

 Mediterranean ; the latter no larger than a grain of sand. 

 2. Pterotrachea. 

 3. Phylliroe. 



These genera, the last of the mollusca, have no shell. 



In parting with our author, we cannot but congratulate and 

 thank him for the essential service he has rendered the science by 

 his admirable work. In his hands conchology has assumed its 

 proper aspect, and from being little better than a vague mass of 

 unconnected descriptions, now forms a regular and important link 

 in the great chain of natural history. If his system be not abso- 

 lutely faultless, it is at least superior to any other general system 

 extant. In one or two instances, perhaps, Lamarck may have con- 

 stituted a genus, from characters not sufficiently peculiar to entitle 

 the individual to that distinction. His castalia, for instance, seems 

 to be separated from the unio on insufficient grounds; and Mr. G. B. 

 Sowerby has, we think very properly, restored it to that genus. 

 Indeed, our author himself appears to have had some doubt on 

 the subject, from the specific name amligua, by which he deno- 

 minates it. 



In point of nomenclature, the work contains some grammatical 

 inaccuracies and iaelegancies, which have occasionally surprised 

 us. The names are frequently taken from obsolete Latin terms, 

 when better words night, just as easily, have been adopted, and 

 much confusion prevails in the genders assigned to several of 

 them. Thus, diceras, derived from a Greek neuter noun, is made 

 eminine ; pterocera, similarly derived, should be pteroceras, and 

 neuter ; as should anostoma, but, like diceras, they are both made 



