OF CONCHOLOGY. 333 



cality. As the (figured) descriptions of Eschscholtz were very- 

 accurate for that time, it is considered that they deserve pre- 

 cedence, especially as the genus was constituted from them. 



The Nuttallian limpets, as well as Chitons, were not de- 

 scribed in Conrad's paper; whether because the author re- 

 garded them as identical with the similar forms from other 

 seas, or because their determination is somewhat difficult, is 

 not stated. However, Prof. Nuttall freely distributed his nu- 

 merous specimens through the principal American and English 

 collections, under well-chosen names for the principal forms. 

 Although these names are of no authority in literature, having 

 been first published, without descriptions, in Jay's Catalogue, 

 it would have saved much confusion if they had been adopted, 

 in preference to new ones, by American authors, as they were 

 by English. Such a mark of courtesy would have been at 

 least a graceful compliment from a pupil to a venerated 

 teacher. However, both the Nuttallian names, when descrip- 

 tions were at last published by Reeve, and those of Gould, 

 must give place to the prior designations of Eschscholtz, al- 

 though some of them may be conveniently retained for va- 

 rieties. 



The Gouldian species do not appear to have been noticed, 

 or, at any rate, were not understood by Mr. Reeve, who, in 

 his Monograph, described almost all the supposed species of 

 Nuttall, from the Cumingian collection, adding some others 

 of his own. The plates and extended descriptions of Dr. 

 Gould's shells, in the Exploring Expedition Mollusca, were 

 scarcely known in Europe till many years after their publica- 

 tion. In fact, the work was not accessible in the Smithsonian 

 Institution in 1859 ; and it was only by special favor that I 

 then obtained a proof copy of the plates, and borrowed the 

 quarto volume from a friend, in order to work- up the Ex- 

 ploring Expedition collections. At that time Dr. I. Lea had 

 not been able to find a copy in Philadelphia, nor to see Dr. 

 Gould's type specimens of Unionidae. It is very greatly to 

 be regretted that the works published by Government are not 

 at once allowed to enter the regular markets, and are not sent 

 as soon as published to the principal libraries of science. 



Most of all shells, it is necessary that limpets be studied 

 geographically. What differences may exist in the animals, 

 we do not as yet know; but, though normal specimens may 

 carry their specific marks along with them, there are every- 

 where, and especially in the different sections of the West 

 American Coast, so many unconformable specimens which 

 closely resemble distant species, that the naming of limpets in 

 a mixed assemblage can never be performed with confidence. 



