24 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



It is not without some reluctance that I have concluded to use Bolton's 

 name Chlamys for this rather large group of recent and fossil shells ; not 

 being quite sure that I have had an opportunity to consult all of the works 

 necessary to decide whether some other may not have better claims to recog- 

 nition. In 1847, Dr. Gray apparently proposed to adopt for such forms Poli's 

 name Argus (1791); but as that name had been used by Scopoli in 1777 

 for a genus of insects, it seems objectionable. 



By most authorities these shells have been generally referred to the 

 genus Pecten, and are even considered, by those who go back to Klein and 

 other pre-Linnaean writers, as the typical forms of the group for which that 

 name should be retained. As I do not believe, however, that we should cite 

 as the authors of genera any pre-Linncean writers, I am unwilling to view 

 Klein as the author of the genus Pecten, although he, as well as other ante- 

 Linnsean writers, used it. Coming down, then, to later authorities, Miiller 

 seems to have been the first regular binomial author who used the name 

 Pecten; and, consequently, he has the best claims to be regarded as the 

 founder of the genus (in 17 76). His first species was Pecten maximus 

 (— Oat tea maxima, Linn.), but he included also other species belonging to 

 other groups. In 1789, Bruguiere adopted the genus, also citing P. maximus 

 fust, though he likewise included species belonging to distinct groups, 

 and hence cannot be regarded as having restricted the genus. In 1799, 

 however, Lamarck adopted the genus, and cited only, as the typical example, 

 P. Jacobceus (z= Ostrea Jacolycea, Linn.), a species acknowledged by all to 

 belong to the same group as P. maximus, to which it is specifically closely 

 related. Consequently, Lamarck should be regarded as having restricted the 

 genus to this particular group, which is, by most authorities, considered 

 generically distinct from that here under consideration ; and, for these 

 reasons, I do not think we can correctly use the name Pecten for the/group 

 here described. 



H. and A. Adams, in their valuable work on the "Genera of Recent 

 Mollusea," use the name Pecten for the types here under consideration 

 placing under it, as subgenera, Chlamys, Dentipecten, and Pseud-amussium. 

 Dr. Stoliczka docs the same, and also includes, in the same way, Lyropecten, 

 Camptonectes, Amussium, and Syncyclonema. Although these groups are all 

 more or less closely related, it seems better to view them all as distinct 

 genera from Chlamys, as here defined. 



