OF CONCHOLOGY. 19 



have given to differentia] characters drawn from the buccal and 

 lingual dentition of Mollusks an important systematic value, we 

 shall name further, in England, Dr. Gray, in America, Mr. 

 Morse, and, finally, in Denmark, our learned colleague Mr. Morch, 

 who has recently published in our Journal* an important article 

 on this subject. 



Although we do not dispute the great learning of our honor- 

 able collaborator, yet we do not entirely agree with him concern- 

 ing the systematic value that should be given to the lingual and 

 buccal dentition of 3IoUusJcs in their classification. He believes 

 this character to be of primai-y value, and that, consequently, the 

 value of teeth in Mollusks must be considered as equal, or nearly, 

 to that of corresponding parts in Mammalia. 



We are far from advocating this opinion, and we beg to show 

 in a few words the reasons which, we think, speak against it. 



In Mammalia, the differential characters drawn from the teeth 

 generally correspond to other important modifications, of the 

 bones, digestive system, the manner in which the members are 

 terminated, — in one word, with one or several other important 

 parts of the organism. 



It is for this reason that they are considered, and with reason, 

 as distinctive characters of the first order. 



Is it the same as to Mollusks ? We think not, and if we must 

 prove it, the proofs will not fail. Let the lingual dentition of a 

 certain number of Mollusks belonging to different genera, how- 

 ever related to each other, be comparatively examined, and it 

 will almost invariably be seen that, in the intimate constitution of 

 these teeth, there are considerable differences, and not at all ac- 

 cording with the slight difference of the other zoological cha- 

 racters. As Mr. Morch himself acknowledges, "the Aeolis and 

 the Valuta have but one row of teeth, while the genera nearest 

 approaching the first of them have numerous rows, and those 

 nearest to the second three rows." Some genera, [Thetis, 

 Stilifer, Leptoconchus, for example,) have no teeth, while the 

 nearest forms have them. 



This last fact is more striking still in the family of the Dori- 

 dopsidae and genus Doridopsis, recently created by Messrs. 

 Alder and Hancock. f 



The Mollusks of this family are so similar to the genuine Doris 

 in their principal characters, that several of them have been 

 described as such without hesitation by authors. [Doris tubercu- 

 losa, Quoy and Gaimard, and D. nigra, Stimpson, for example.) 



* "Journal de Coachyliologie," 1865. 



f Notice of a Coll. of Nudibranchiate MoUusea made in India, &c. Trans, 

 of the Zool. Soc. of London, 1864. 



