CLASS PELECYPODA 
67 
Type in Museum Cuming. Type locality, Panama. 
Range. Santa Barbara, California, to Panama and Galapagos Islands. 
Genus SEPTIFER Recluz, 1848. 
Shell equivalve, very inequilateral; ventral margins sub-concave and 
cut out for the passage of the byssus; beaks sub-terminal, curved; hinge 
without teeth, furnished with a lamellar septum; ligamental pits linear, 
marginal, dorsal, anterior, with a white, nearly spongy margin within; 
muscular impressions superficial, the anterior small, rounded, the posterior 
large, subdorsal, uniform. 
Type not known to the writer. 
Distribution. Warm seas. 
Range in time. In the Silurian, Carboniferous and Permian of 
Europe. In the Pleistocene at Santa Barbara, San Pedro, and San Diego, 
California. 
Septifer bifurcatus (Conrad) Reeve, 1837. 
Jour. Acad. Nat. Sci. Phila., 7 :241; pi. 18, fig. 14. 
Shell narrowed, slightly arcuate; anterior margin much flattened; ribs 
narrow, prominent, bifurcated toward the base; color dark purple. Height 
1 y 2 inches. (Conrad.) 
Type in Phila. Acad. Nat. Sci.? Type locality, Oahu, Hawaiian Islands. 
Range. Crescent City, California, to the Gulf of California. 
Septifer bifurcatus obsoletus Dali, 1916. 
Proc. U. S. N. M., 52:404. 
Shell large, the external sculpture obsolete, the distal part of the valves 
nearly smooth. (Dali.) 
Type in U. S. N. M., No. 173359. Type locality, San Diego Bay, mud 
flats. 
Range. Known only from the type locality. 
Genus MODIOLUS Lamarck, 1799. 
Shell oblong equivalve, more or less ventricose, with the umbones 
small, rather swollen, not terminal, anterior side often expanded, posterior 
arched, contracted. Hinge linear, with the ligament marginal and partially 
internal. Muscular impression compound, sub-lateral. 
The typical distinction between Mytilus and Modiolus consists in the 
latter having a lighter and more cylindrical, oblong shell, with the umbones 
rounder and not terminal, in consequence of the posterior extremity of 
the shell projecting beyond them. (Reeve.) 
Type. Modiolus modiolus (Linnaeus.) 
