460 Systematic Paleontology 



Genus AVICULA Klein 



AvicuLA kecticosta Hall? 



Plate LXXVI, Fig. 7 



Avicula rccticosta Hall, 1859, Nat. Hist. N. Y., Pal., vol. ill, p. 466, pi. cix, 

 fig. 3, 1861. 



Description. — " Shell slightly oblique, subrhomboidal : hinge-line 

 greater than the greatest width of the shell below; width equal to about 

 once and a third the height, very moderately convex. Posterior wing large, 

 extending nearly as far backwards as the posterior margin of the shell. 

 Anterior wing smaller, triangular, slightly concave on the outside. Sur- 

 face marked by strong dichotomizing subequal ribs, which proceed prin- 

 cipally in pairs from the umbo to the margin of the shell. Posterior wing 

 with fine radiating ribs and close concentric laminae; the anterior wing 

 being marked only by the concentric striae." Hall, 1859. 



To this species is referred, doubtfully, a single fragmentary individual. 



Occurrence. — Oriskany Formation. Locality unknown. 



Collection. — Eobert H. Gordon. 



[Ohern.] 



Section ISODONTA 



Family PECTINIDAE 



Genus AVICULOPECTEN McCoy 

 AvICULOPECTEN ( ?) CUMBERLANDENSIS n. Sp. 



Plate LXXVIII, Fig. 3 



Description. — Shell subcircular, length and height about equal ; slightly 

 oblique ; left valve gibbous, the maximum inflation being anterior to the 

 center of the shell which curves thence steeply to the anterior, and much 

 less so to the basal and posterior margins ; anterior margins broadly sinuate 

 at junction of anterior wing and the body of the shell, thence slightly 

 convex outward to anterior extremity, thence the margin is almost semi- 

 circular to the posterior wing which is widely sinuate, the maximum ex- 

 cavation being at about two-thirds the distance from the extremity of the 

 wing to the body of the shell ; anterior wing small, concave ; posterior wing 



