42 
nated and posterioriy become extinct; vaives radiantly ribbed. 
which also become obsolete at the posterior end; at the inter- 
section of the radiating and concentric lines the sculpture is 
pectinated; an area below the umbos, nearly or quite destitute 
of sculpture, which varies much in prominence in different 
specimens; accessory plate sub-lanceolate and bent down on the 
beaks, anteriorly prolonged over but not covering the ante- 
umbona! gape; interior of valves white enamelled; interna! rib 
short, curved and flattened. Largest specimen, two and six- 
tenths inches in length, and one and five-tenths inches in height. 
Habitat—Atameda, San Francisco bay, California, where in 
some places it is common in sandy mud_ between tide 
marks. Numerous specimens collected by Messrs. Harford, 
Hemphill, Drs. Kellogg and W. P. Gibbons.’”’—Roberi KE. C. 
Stearns, Conchological memoranda No. 7 (28 Ag 1871) Ca ae pr 
5 :—+t 1. 16, 6a, 6b, 6c, (7 Ap 1873). 
Mrs. Williamson (U S Na mu pr 15: 183), reports “three 
or four washed ashore with the tide” at —_ Pedro bay, Califor- 
nia, and adds “single valves not plentiful.’ 
PTYCHATRACTUS OCCIDENTALIS 
“Shell elongated, fusiform, rather slen ‘er, whitish, traversed 
by narrow( revolving, brownish threads and much wider inter: 
vening spaces; suture distinct, spire tapering; aperture ob’ong 
oval, abont halt the length of the shell; within white, poitshed: 
canal short, nearly straight; columellar obliquely, not strongiy 
plicated; length about three-fourths of an inch. Habitat—near 
the Island of Attcu, at the west end of the Aleutian 
Archipel- 
ago.”—Robert I. 
C. Stearns, Concho! ogical memoranda No. 
7 (28 Ag 1871): Ca ac pr 5 :— (7 Ap 1873) :—“‘Habitat—near . he 
Island of Nagai, one of the Shumagin Is!ands, where it was 
hooked up attached to a rock from a depth of 40 fathoms, by 
Captain Prime of the Ca‘ifernia Fishing F eet; through the kin1- 
