156 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 37. 
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. 
Species 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. equata Conrad, 
of the Virginia Miocene. It is named for Mr. R. KE. 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 
Dosimia dunkeri; beaks small, pointed, slightly prosoceelous, adja- 
cent; anterior end evenly rounded; posterior end slightly subtrun- 
cate, straighter, a little produced near the base, which is evenly 
arcuate; ligament strong, somewhat sunken; hingeplate excavated; 
teeth two in each valve, the anterior in the léft and the posterior in 
the right valve larger and bifid; pallial line entire, margin simple, 
muscular sears small. Length, 12.0; height, 11.5; diameter, 6.0 mm. 
This form has a rather unusual sculpture and polish for a Dziplo- 
donta, the yellowish periostracum is slightly zoned with pale gray. 
It has, like other shells of its size, no economic relations. 
Type-specimen.—Cat. No. 207758, U.S.N.M. 
CHAMA PELLUCIDA Broderip. 
Chama pellucida Broperip, Trans. Zool. Soc. of London, vol. 1, 1835, p. 302, 
pl. 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 by 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. 
