120 CALIFORNIA ACADEMY OF SCIENCES. 



Genus Modiolus Lanuirck-. 



Shell oblong, inflated in front; umbones anterior obtuse; hinge toothless; pedal impressions 

 three in each valve, the central elongated; epidermis often produced into long beard-like fringes. 



Type, Mytilus modiolus Linne. 



Section ilodiolus s. s. ' 

 Surface smooth, shell inflated, edentulous, epidermis more or less hirsute. 

 Type, Mytilus modiolus Linne. 



42. Modiolus fornicatus Carpenter. 



Modiola fornicaia Cpr., Brit. Assn. Rep., 1863, p. 643; Ann. cS: Mag. Nat. Hist , 3rd Ser., Vul. 

 XV, 1865, p. 179. Keep, West Coast Shells, p. 173, 1892. Williamson, Proc. 

 U. S. Nat. Mus., Vol. XV, 1892, p. 191. 



Shell of medium size, short, oblong, inflated in front, swollen, equivalve; beaks anterior, 

 not quite terminal, obtuse, marginal, bent forward; surface sculptured only with concentric incre- 

 mental lines; margins smooth; no hinge teeth. 



Dimensions. — Beaks to ventral margin 54 mm.; lat. 31 mm.; diam. 30 mm. 



This species is distinguishable by its short, swollen form. 



Rare in the lower San Pedro series of Deadnian Island, and in the upper San 

 Pedro series of Los Cerritos. Found also in the Pleistocene of Bai'lovv's ranch, 

 Ventura, and bluff west of bath-liouse, Santa Barbara. 



Liviny. — Monterey to Santa Barbara (Carpenter): San Pedro (Williamson). 



Pleistocene. — San Pedro (Ai'nold): Ventura; Santa Barbara (Arnold). 



43. Modiolus rectus Conrad. 



Modiola recta CoN., Journ. Acad. Nat. Sci. Phil., Vol. VII, 1837, p. 243, pi. XIX, fig. i. Carpenter, 



Brit. Assn. Rept., 1863, p. 643. Gabb, Pal. Cal. Vol. II, p. loi, 1869. Cooper, 7th 



Ann. Rept. Cal. St. Min., 1888, p. 251. Keep, West Coast Shells, p. 171, fig. 145, 



1892. Williamson, Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 192. Dale, Trans. 

 Wagner Inst. .Sci., Vol. Ill, Part. 4, i8yS, p. 793. 



Shell large, rhomboidal, narrow, evenly convex, not sharj^ly ridged, sculptured by numerous 

 fine, concentric, incremental lines; lower margin a nearly straight line; ligament long, narrow, 

 straight. 



Dimensions. — Long. 150 mm.; alt. 50 mm.; diam. 38 mm. 



Specimen identified by Dr. Dall. 



Rare in lower San Pedro series of Deadman Island, and the upper San Pedro 

 series of Deadman Island, San Pedro, and Los Cerritos. Found also in the Pliocene 

 of Pacific Beach, and the Pleistocene of Pacific Beach and Twenty-sixth Street, 

 San Diego. 



Living. — Santa Cruz to San Diego (Cooper). 



