180 Kansas Academy of Science. 



6. Phacoides cf. nuttallii Conrad. Plate I, fig. 6. 



Only a cast was obtained. Shell small, orbicular, slightly con- 

 vex; umbones depressed, small, central; surface marked by numer- 

 ous concentric lines and radiating ridges. 



Specimen obtained from the Oligocene-Miocene formation near 

 Neah Bay, Wash. This is the cast figured in the plate.^^ 



Family XXIII Cryptodontid^; Genus Thyasira. 



"Shell globular, posterior side furrowed or angulated; umbones 

 much recurved; lunule short or indistinct; ligament usually and 

 to a certain extent external, placed in a groove on the hinge line, 

 and outside the hinge-plate; teeth altogether wanting." (Arnold.) 



7. Thyasira bisecta Conrad. Plate I, fig. 7. 



Venus bisecta Con., Wilkes's Expl. Exped., vol. X, p. 724, pi. XVII, figs. 



10-lOa, 1849. 

 Thyasira bisecta Con., Meek, Smithsonian Check List, Miocene Fossils, 1864. 

 Cyprina bisecta Con., Jour. Conch., 1865, p. 153. 

 Conchocele bisecta Con., Gabb, Pal. Cal., vol. II, p. 99, 1869. 

 Conchocele disjuncta Gabb, Pal. Cal., vol. II, pp. 28-29, pi. VII, fig, 48, 1869. 



Cooper, 7th An. Rept. Cal. St. Min., 1888, p. 236. 

 Cryptodon bisectus Con.. Dall, Proc. U. S. Nat. Mus., vol. XV, 1892, p. 189; 



vol. XVII, 1894, p. 713, pi. XXVI, figs. 2-5.39 

 Thyasira bisecta Con., Arnold, Mem. Cal. Acad. Sci., vol. Ill, pp. 135-136, 



pi. XV, fig. 5. 



Shell large, subquadrate, subrhomboidal, ventricose, convex, of 

 medium thickness; anterior end very short, abruptly truncate, an- 

 gulate below, with submarginal ventral furrow and the inferior 

 margin at its termination slightly excavate; cardinal margin arched, 

 sloping downwards towards the posterior end; surface strongly ex- 

 cavate from upper side of the beak to the posterior margin and 

 subcarinate below the excavation; beaks terminal, anterior pointed 

 forward; ligament long, elliptical, forming a regular curve with the 

 supero-posterior margin; large lunular area in front of beaks; 

 basal margin generally arcuate. 



A single specimen was obtained in an exposure on the beach- 

 front near Neah Bay on the Strait of Juan de Fuca. 



Living: Puget Sound, sixty-nine fathoms (Dall). 



Pliocene: San Pedro, Cal. (Arnold). 



Miocene: Astoria, Ore. (Conrad); Blakely, near Seattle, Wash. 

 (Arnold). 



Oligocene-Miocene : Neah. Bay, Wash. ; on the Pacific coast, three 

 and one-half miles south of the mouth of the Quillayute river, 

 Clallam county, Washington (Reagan). 



38. A shell resembling Phacoides anmdatus Reeve also occurs in this formation. 



39. After Arnold, loc. cit. 



I 



