NEOZOIC INVERTEBRATES 117 



Mya crassa Grewingk. 



Mya crassa GREWINGK, Beitrag NW. Am., p. 282, pi. vr, figs. 2a-2d, 1850. 



Localities. Unga Island; and near the Pavlof volcano, on the 

 Peninsula of Alaska (Grewingk). 



A large, heavy, subtriangular form, possibly a mutation of the fol- 

 lowing species. 



Mya arenaria (L. ?) Grewingk. 



Mya arenaria GREWINGK, Beitrag NW. Am., p. 283, pi. vr, figs. 3a~3c, 1850. 



Locality. Unga Island (Grewingk). 



The true Mya arenaria seems unknown from the Pacific coast, ex- 

 cept as introduced with seed oysters in the recent fauna. The form 

 analogous to it, but which is never exactly the same, has often been 

 cited as arenaria and also under a name Mya prcecisa, which Gould 

 gave to a mutation of Mya truncata L., but it is probable that the 

 name crassa bestowed as above by Grewingk will have to be retained 

 for it, as in collections of the recent form I have found both the typi- 

 cal M. crassa and that which Grewingk called arenaria to be united 

 by intermediate mutations. 



Mya truncata Linne 1 . 



Mya truncata LINNE, Syst. Nat., Ed. x, p. 670, 1758. LYELL, Trans. Geol. 

 Soc. Lond., vi, p. 137, pi. xvn, figs. 5-6, 1841. GREWINGK, Beitrag 

 NW. Am., p. 283, 1850. 



Localities. Unga Island, Kadiak Island, and the vicinity of the 

 Pavlof volcano, on the peninsula of Alaska (Grewingk). Also in the 

 Pliocene, Pleistocene and recent faunas abundantly. 



Saxicava tingana Grewingk. 



Saxicava ungana GREWINGK, Beitrag NW. Am., p. 281, pi. vi, figs. la-ic, 

 1850. 



Locality. Unga Island (Grewingk). 



It is somewhat doubtful if this is distinct from the S. arctica L., 

 but not having seen specimens I retain the name for the present. 



Teredo ? sp. 



Locality. Popof Island, 3372. 



Casts of large borings resembling those of Teredo and having an 

 average diameter of 19 mm., were obtained. They appear to have 

 had originally a circular section but are somewhat distorted by pressure. 



