12G CALIFORNIA ACADEMY OF SCIENCES. 



51. Mytilimeria nuttalli Conrad. 



Plate XVII, Fig. 8. 



Mytilimeria tnMa/ii Con., }ourn. Phil. Acad. Sci., Vol. VII, 1837, p. 247. Cpr., Brit. Assn. Rept., 

 1863, p. 638. Gabb, Pal. Cal., Vol. II, p. 90, 1869. Tryon, Syst. Conch., Vol. Ill, 

 1884, p. 147, PI. CVIII.fig;. 68. Cooper, 7th Ann. Rept. Cal. St. Min., 1888, p. 252. 

 Keep, West Coast Shells, p. 203, 1892. 



Shell small, equivalve, suboval, convex, thin; beaks central, subspiral, small; surface sculp- 

 tured by fine, concentric, incremental lines and numerous delicate radiating sulcations, the whole 

 having a pearly luster; hinge edentulous, with a slight linear cavity under the beaks; pallial sinus 

 broad, obtuse. 



Divicnsio7is. — Long. 11 mm.; alt. 17 mm,; diam, 10 mm. 



Thi.s fragile little shell resembles a very small and broad Mytilns, but is easily 

 distinguishable by its delicate scnlptnre. Specimens identified by Dr. Dall. 



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

 the lower San Pedro series of San Pedro. 



The species figured is imperfect. It came from the lower San Pedro series at 

 Deadman Island, and is now in the collection of Delos Arnold. 



Living. — Straits of Fnca to San Diego (Cooper). 



Pleiaiocene. — San Pedro (Cooper; Arnold). 



Miocene. — Tomales, Marin County (Cooper). 



Superfamily POROMYACEA. 

 Family XVII. VERTICORDIIDiE. 



Genus Verticordia S. Wood. 



Shell suborbicular, with radiating ribs; beaks subspiral; margins denticulated; interior 

 brilliantly pearly; hinge with one prominent cardinal tooth in each valve; adductor scars two, faint; 

 pallial line simple; ligament internal, oblique; epidermis dark brown. 



Type, Verticordia cardiiformis Wood. 



52. Verticordia novemcostata Adumi^ <£• Reeve. 



Plate XVII, Fig. 10. 



Verticordia nove^ncostata Ad. & RvE,= V. oriiata D'Orb. (yza'f Cpr., Brit. Assn. Rept., 1863, p. 645.) 



Shell small, suborbicular, compressed, thin; beaks subcentral, subspiral, small, sharp, 

 anterior extremity evenly rounded; posterior dorsal margin evenly arcuate, and joining arcuate 

 ventral margin in an angular extremity; surface with nine prominent, sharp, arcuate, radiating ridges; 

 the first and third interspaces wider than the others; margins sharply denticulate; liinge with one 

 prominent cardinal tooth in each valve; adductor scars two, faint; pallial line simple; ligament 

 internal, oblique; interior pearly. 



Dimensions. — Long. 4 mm.; alt. 3.5 mm.; diam. 2 mm. 



