m. U WHITE ON JURA-TRIAS FOSSILS OF IDAHO. 109 



made at locality IS'o. 1 there are several examples of anotlier species of 

 Terebmtula wliicli were obtained from member A of the foregoing section, 

 the same member from which T. semisimplex was obtained, but it comes 

 from a different, although near layer. These possibly belong to a new 

 species, but they answer too closely to the figures and description of T. 

 augtista, as given by Hall and Whitfield in Vol. IV of the United States 

 Geological Survey of the Fortieth Parallel, to make it advisable at present 

 to propose a new name. The original locality of T. augusta is at Sho- 

 shone Springs, Aiigusta Mountains, ISTevada ; and the strata from which 

 it comes are assigned to the Jurassic in the reports just cited. Collected 

 by Dr. A. C. Peale. 



CONCHIFEEA. 



Genus Aviculopecten McCoy. 



AviGULOPECTEN PEALEi White. — Shell, exclusive of the ears, sub- 

 ovate in marginal outline; obliquity of the axis to the hinge-line back- 

 ward, and forming with it an angle of about 70 degrees ; hinge-margin 

 not quite as long as the greatest transverse diameter of the body of the 

 shell. Left vah^e moderately convex, the convexity being nearly uni- 

 form, except in the umbonal region, where it is, as usual, greatest ; beak 

 moderately prominent, incurved, and elevated slightly above the hinge- 

 margin ; anterior ear moderately large, prominent, extending as far for- 

 ward as the front margin of the shell, distinct from the body of the 

 shell, but not separated from it by a distinct auricular furrow ; its antero- 

 inferior border convex, sloping backward to a moderately deep, angTdar, 

 byssal notch ; front margin of the valve regulaily convex; antero- basal 

 margin convex, but not quite so much so as the front ; postero-basal 

 margin somewhat abruptly rounded up to the nearly straight posterior 

 margin. Posterior ear moderately large, but not quite so prominent as 

 the anterior ear, moderately distinct from the body of the shell, its pos- 

 terior margin forming nearly a right angle with the hinge-margin, and 

 a very obtuse one with the posterior margin of the body of the shell. 

 Surface marked by numerous raised radiating lines and small costoe, the 

 latter beiiig less numerous than the former, and differing from them only 

 in being larger, all of them being slightly undulating in their direction 

 from the umbo toward the margin. ISTear the margins three or foiu- of 

 the lines occupj^ each of the spaces between the costte. Both ears are 

 marked by radiating raised lines similar to those on the body of the 

 shell, but they are more numerous and finer on the posterior ear than on 

 the anterior. Crossing these radiating lines and costoe, there are numer- 

 ous fine, but distinct, concentric lines, and some larger wrinkles of 

 growth. Eight valve unknown. 



Height from base to beak, 37 millimeters ; anteroposterior diameter 

 of the body of the shell, 33 millimeters ; length of hinge-margin, 28 mil- 

 , limeters. 



