156 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. r,7 



the surface seems very liable to injury with resulting irregularities 

 and depressions not normal to the shell; ligament strong, internal, 

 its surface with a slight limy coat not consolidated into a lithodesma; 

 hinge line edentulous, with a small callosity immediately in front of 

 the ligament; pallial line entire, faint; interior of the valves white 

 and smooth. 



The type (Cat. No. 207759, U.S.N.M.) measures: Length, 7.5; height, 

 6.5; diameter, 6.5 mm. 



Si)ecies of this genus exist on the east coast of the United States, 

 and in the southern Tertiaries from the Eocene up; but this is the 

 first time it has been recognized from the Pacific coast of the Ameri- 

 cas. The present species is very similar to the A. sequata Conrad, 

 of the Virginia Miocene. It is named for Mr. R. E. Coker. 



DIPLODONTA (FELANIELLA) ARTEMIDIS. new species. 



Plate 28, fig. 8. 

 On the "inside" or lagoon beach at Capon, in the sand. 



Shell small, rather compressed, suborbicular, slightly inequivalve, 

 the posterior side shorter; white with a polished yellowish perios- 

 tracum and concentric sculpture, recalling in miniature that of 

 Dosinia dunkeri; beaks small, pointed, slightly prosocoelous, adja- 

 cent; anterior end evenly rounded; posterior end slightly subtrun- 

 cate, straighter, a little produced near the base, wdiich is evenly 

 arcuate; ligament strong, somewhat sunken; liingeplate excavated; 

 teeth two in each valve, the anterior in the left and the posterior in 

 the right valve larger and bifid; pallial line entire, margin simple, 

 muscular scars small. Length, 12.0; height, n.5; diameter, 6.0 mm. 



This form has a rather unusual sculpture and polish for a Biplo- 

 donta, the yellowish periostracum is slightly zoned with pale gray. 

 It has, like othei' shells of its size, no economic relations. 



Type-specimen.— QAii. No. 207758, U.S.N.M. 



CHAMA PELLUCIDA Broderip. 



Chama pelludda Broderip, Trans. Zool. Soc. of London, vol. 1, 1835, p. 302, 

 pi: 38, fig. 3. 

 On the shore rocks at the island of Lobos de Afuera, and at Matacaballa, Sechura 

 Bay, Peru. 



Distribution. — From California south to Chile and Juan Fernandez 

 Island. 



Shell coarse, irregular, variable in form, adherent b}^ the whole of 

 one valve to rocks or other objects; rounded, the valves more or less 

 subspiral; white with occasional reddish streaks on a subtranslucent 

 ground; white within, with a crenulated margin; the exterior rude 

 or rough, often much eroded, sometimes lamellose under favorable 

 conditions of growth, reaching 2 inches in diameter, but having no 

 economic value. 



