1918] Packard: Molluscan Fauna from San Francisco Bay 283 
Schizothaerus Conrad 
Schizothaerus nuttalli (Conrad) 
Plate 28, figures la and 1b 
Lutraria (Cryptodon) nuttalli Conrad (1837), p. 235, pl. 18, fig. 1. 
Tresus nuttalli, Arnold, R. (1903), p. 178. 
Schizothaerus nuttalli, Carpenter (1863), p. 640; Wood and Raymond 
(1891), p. 55. 
Description.—This species was originally described by Conrad as follows: 
‘*Shell elliptical, slightly gibbous from beak to base; posterior side pro- 
duced; ligament margin slightly declining, rectilinear, extremity obliquely sub- 
truncated; umbo prominent; color white; epidermis very thin, brown, wrinkled 
on the margins.’’ 
Length, 7 to 130 mm. 
Occurrence.—At stations D 5700 (2 
D 5710) (£:), D 5712* (2), D 5713 (1), D 5732 €.), D 5738 (£.), D 5740 
(1), D 5749* (10), D 5766 (1), D 5778 (2), D5795 (3), D 5796 (2), 
D5798 (1), D5801 (3), D5808 (10), D5809 (10), D5821 B (1), 
D 5826 (3), D 5827 (3), D 5833 (f.), D5827 A (2), D5827 B (2), 
D 5828 B (f.), D 5829 A (3), D5844 (6), Sausalito shore (7), and 
questionably at D 5752 and D 5760. 
This species burrows deeply, and therefore was taken alive by the 
dredge but once. Specimens were taken by the Survey only at the 
outside stations and those within the middle portion of the bay. Shells 
were dredged from depths up to 60 fathoms. 
Dall recognizes the variety capar Gould as ranging from Kadiak, 
Alaska, to San Francisco. 
Range.—The typieal species, including the Alaskan variety, ranges 
from Kadiak Island to Todos Santos Bay, Lower California. 
MyacrEa 
MYACIDAE 
Mya Linnaeus 
Mya arenaria Linnaeus 
Plate 29, figures la and 1b, plate 52 
Mya arenaria Linnaeus (1758), p. 670; Gould (1841), p. 40; Tryon (1873), 
p. 140; Stearns (1881), p. 362; Woo and Raymond (1891), p. 55. 
Mya hemphilli Newcomb (1874), p. 415. 
Description.—Gould (1841) described this species in the following terms: 
“‘Shell transversely ovate, subequilateral, convex, gaping at both ends, 
but more so at the posterior end where the valves curve outwards. Beaks 
small, epidermis rough, wrinkled, yellowish.’’ 
Length, 2 to 110 mm. 
