216 GENUS SCALPELLUM. 



Gray lias proposed or adopted generic names for four of 

 the species, and a fifth certainly has equal claims to this 

 same rank. These genera have been founded almost 

 exclusively on the number of the valves ; and oddly 

 enough, the numbers have generally been given wrongly, 

 namely, in Scalpellum, Calantica, Thaliella, and Xiphi- 

 dium. Scalpellum blends through S. villosum into 

 Pollicipes ; and this latter genus has an equal right with 

 Scalpellum, to be divided into sub-genera, three in number. 

 Hence, no less than eight genera might be made out of the 

 twelve recent species of Scalpellum and Pollicipes, and 

 their formation, in some degree, be justified ; but, in my 

 opinion, this inordinate multiplication of genera destroys 

 the main advantages of classification. At one time, I 

 even thought that it would be best to follow Lamarck, 

 and keep the twelve recent species in one genus ; but 

 considering the number of fossil species, I believe the 

 more prudent course has been followed, in retaining the 

 two genera Scalpellum and Pollicipes ; more especially 

 as I can hardly doubt, that several other species will be 

 hereafter discovered. 



Having so lately described in the Memoirs of the 

 Palseontographical Society, the fossil species, I will not 

 here further allude to them, than to state, that out of the 

 fifteen species therein described, S. magnum comes very 

 close to the recent S. vulgar e, and that several Eocene 

 and Cretaceous species, such as S. quadrat urn 7 S. fossula, 

 and S. maximum, are allied to S. rutilum and S. ornatum. 

 Scalpellum villosum, a recent species, has stronger claims 

 than any other species to be generically separated ; and 

 its habits, in not being attached to horny corallines, are 

 also different, but the identity of its Complements Male 

 with that of S. Peronii, and its numerous points of resem- 

 blance in structure with the other species, have deter- 

 mined me not to separate it. Scalpellum Peronii, villo- 

 sum, and rostratum, in having a sub-carina, — in the 

 rostrum being pretty well developed, — and in the Com- 

 plemental Male being pedunculated, and furnished with 



