1918 ] Packard: Molluscan Fauna from San Francisco Bay 259 
This southern species is represented by two living individuals 
dredged from the dark green sands outside the Golden Gate at depths 
of from 46 to 68 fathoms. The specimen that was questionably re- 
ferred to this species was dredged in 8 fathoms of water north of 
Angel Island. 
Range.—Bodega Head, California, to Cerros Island, Lower Cali- 
fornia (Dall). 
Modiolus modiolus (Linnaeus) 
Mytilus modiola Linnaeus (1767), p. 1158. 
Modiola modiola, Tryon (1873), p. 186, pl. 39, figs. 510, 511. 
Description.—This species is described by Tryon as follows: 
“«Shell large, coarse, and solid, oblong, obliquely dilated; beaks tumid, ob- 
tusely angulated; basal margin concave, with a fissure for the byssus; surface 
coarsely marked by growth lines; epidermis thick, dark violaceous, blackish, 
or chestnut brown; within pearly. Animal dark-orange or reddish, edible.’’ 
This species was not obtained from these waters by the ‘‘ Alba- 
tross,’’ although it has been reported from this region by Cooper. 
Range—Arectic Sea to San Pedro, California (Dall), Atlantic 
Coast south to Cape Hatteras (Rogers). 
Modiolus, sp. 
Several immature specimens of Modiolus are among the collections. 
They have not been determined specifically. 
Length, 3 to 10 mm. 
Occurrence—At stations D 5723 (1), D5727 (3), D5738 (8), 
Sausalito (1), Bonita Point (7). 
DREISSENSIIDAE 
Septifer Recluz 
Septifer bifurcatus Reeve 
Septifer bifurcatus Reeve, Carpenter (1863), p. 643; Cooper (1870a), 
p. 54; Dall (1898¢), p. 789; Williamson (1898), p. 67; Arnold, R. 
(1903), p. 119; non Mytlus bifurcatus Conrad. 
Description.—This species was described by Arnold (1903) as follows: 
“*Shell small, wedge-shaped, equivalve, convex, rather thick, beaks pointed, 
terminal; surface sculptured by numerous strong, rounded, terminally bifur- 
cating, radiating ridges, and fine concentric, incremental sulecations; margin 
corrugated; a small lamellar deck stretches across the interior of tke shell near 
the umbo; teeth small.’’ 
