CREPIDULA. Panama Shells. 231 



Crepidula unguiformis Brod. in Trans. Zool. Soc. Lond. I. pi. 29. 



f. 4. 1835. 

 - Mull. Syn. Nov. Test. Viv. p. 151. May 1836. 

 Lam. An. sans Vert. VII. 643. No. 4. 



(Desh. ed.) 1838. 



Pot. etMicli. Gal. Moll. Mus. Douai.I. 514. 1838. 



plana Gould Invert. Mass. p. 159. f. 16. 1840. 



unguiformis Lam. An. sans Vert. III. Pt. 1. p. 236. 



(Desh. ed. tert.) 1841. 



Reeve Conch. Syst. pi. 143. f. 6. 1842. 



- dilatata No. 4. Orb.Voy. Amer. Merid. Moll. p. 467. 1 843. 



- plana Dekay Zool. of N. Y. Moll. p. 158. pi. 7. 



f. 153. a. b. 1843. 



This shell is well calculated to confound the popular notion 

 of species. We have now before us many perfect specimens 

 from Sicily, from Massachusetts, from Jamaica, and from Panama, 

 all of which, with the exception of the Mediterranean shells, 

 we collected in person. They present many modifications of 

 form dependent on progress of growth, and the positions which 

 they occupy in dead shells. But we have in vain attempted to 

 discover any characteristics of locality. The only approach to a 

 local character is to be found in a few of the Panama shells, which 

 have longitudinal rays of reddish brown, while all the other 

 specimens are of a uniform white. So far at least as the shells 

 are concerned, it seems necessary to admit that they all may be 

 comprised in one species ; or to maintain that individuals, which 

 cannot be distinguished from each other, belong to different 

 species, because it is probable that they descended from distinct 

 original stocks. But if we admit that each species in the animal 

 kingdom was introduced by the creation of many original stocks, 

 then the fact before us becomes intelligible and very uncommon 

 in only one particular, viz : that the original individuals of a 

 single species were created in very distant zoological provinces. 



On the opinion that the North American C. plana Say is 

 identical with the Mediterranean C. unguiformis Larn., Dr. 

 Gould remarks as follows : 



"In this opinion I have the concurrence of Mr. Sowerby. 



