of Europe and North America. 21 1 



Again, he states that Area transversa is a variety of Area 

 pexata, the former being put down as northern, the latter as 

 southern. That these shells are widely different in form and 

 in the structure of the hinge is well known ; for Dr. J. E. Gray 

 many years ago established a new genus [Argina) for the 

 latter on account of its very peculiar hinge. That the animals 

 are also quite different I can assert from personal observation. 

 Moreover the differences in the hinge, epidermis, and form 

 are remarkably constant ; and, finally, the two species have 

 the same geographical range from Cape Cod to South Carolina, 

 and are often found together. Both are very common in Long- 

 Island Sound and New-Haven harbour ; and I have examined 

 hundreds of specimens of both species without finding the 

 slightest evidence in favour of Mr. Jeffreys's views. Indeed 

 they are only distantly related, and evidently belong to distinct 

 genera, Argina and Scapharca^ where several writers have 

 placed them. 



He also states that Mactra ovalis is a variety of M. solidis- 

 sima. He may not have seen a specimen of the true ovalis^ 

 for it is not common in collections ; but the genuine ovalis is 

 certainly a very well-marked species, widely different from the 

 solidissima. They differ greatly in the hinge, epidermis, form 

 of shell, and position of the umbos ; moreover the animals are 

 also quite different. Both occur together of equal size in the 

 Bay of Fundy ; but the former is not known south of Cape 

 Cod, while the solidissima is abmidant everywhere along our 

 sandy shores to South Carolina. 



Concerning Astarte castanea he says, " Perhaps a variety 

 of A. horealisj Ch. ;" but castanea is one of the best-defined 

 species in this difficult genus, varies comparatively little, and 

 does not extend far north, its range being decidedly southern. 

 It is perfectly distinct from A. horealis. He reduces A. qua- 

 drans to a variety of A. castanea^ and gives it a name that is 

 quite uncalled for, even if this view were correct. He then 

 makes A. portlandica a variety of A. compressa; but I have 

 already shown (Amer. Jom-n. of Science, April 1872) that it 

 is a variety of A . quadrans. His arrangement of the other 

 species oi^ Astarte is equally objectionable, but it is not necessary 

 to discuss them here. 



The Pecten fusns, Linsley, is given as the young of 

 P. irradians, from which it is very distinct ; but the writer 

 has shown (Aracr. Journ. of Science, vol. ii. p. 361, and 

 vol. iii. p. 213, 1871-72) that it is really the young of P. 

 tenuicostatus. 



Dekay is given as the authority for yEoJis salmonacea and 

 yE. gymnota ; but they were both described by Couthouy in 



14* 



