NEOZOIC INVERTEBRATES 
117 
My a crassa Grewingk. 
Mya crassa Grewingk, Beitrag NW. Am., p. 282, pi. vi, 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. vi, 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 frcecisa, 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 Linnd. 
Mya truncata Linne, Syst. Nat., Ed. x, p. 670, 1758. —Lyell, Trans. Geol. 
Soc. Lond., vi, p. 137, pi. xvii, 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 ungana Grewingk. 
Saxicava ungana Grewingk, Beitrag NW. Am., p. 281, pi. vi, figs, ia-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. 
