334 PROCEEDINGS OP THE NATIONAL MUSEUM. vol.45. 



Genus PTERINEA Goldfuss. 



PTERINEA (?TOLMAIA) TRESCOTTI WUliams. 

 Plate 29, figs. 14, 15. 



Shell of medium size, rhomboidal, body oblique, longitudinal axis 

 at an angle with the hinge line of about 60°; length greater than 

 height; valves unequal; left valve convex; right valve concave from 

 beak to base, gently convex transversely across upper part but flat 

 near basal margin. Hinge line straight, part behind beak nearly 

 four times as great as that in front. Left-valve beak prominent, 

 upright at origin, convex over umbonal region. Body convex, 

 arcuate, anterior side more elevated than posterior, abruptly bounded 

 both on anterior and posterior sides. Anterior ear strong, set off from 

 body by deep rounded furrow; byssal sinus sharply defined, posterior 

 wing triangular produced into short mucronate point at cardinal 

 extremity, distinctly separated from body, posterior margm concave. 

 Rio-ht valve broad, concave from hinge to base line, across center of 

 shell from posterior side slightly convex, beak depressed, not protrud- 

 ing beyond cardinal margm. The surface markings on the left valve 

 are composed of two sets of elevated radiating rays, the stronger set 

 strong cord-like rays evident from front side of body to the extremity 

 of w^ing, the finer set thread-like lines in bottom of furrows separating 

 stronger rays; these are about a millimeter apart over center of body 

 of shell. On the wing and posterior half of the body the secondary 

 rays are absent from the upper half of the surface; on lower half the 

 second series appear between the first set; on the anterior half of the 

 body the secondary rays are evident well up upon the umbonal sur- 

 face, and are sub-equal to the first set toward the base, where both 

 sets appear to be lamellose. The rays are crossed by concentric Imes 

 which become lamellose over the anterior ear. Surface of right valve, 

 as seen in a mold of the interior, is smooth with faint indication of 

 radiating lines on basal haK of body, crossed by a few broad concen- 

 tric growth lines. 



Teeth, anterior to beak are two to four strong, oblique, short teeth; 

 posterior to beak two elongate lateral teeth on right valve curving a 

 little inward toward posterior end, terminating about half way out on 

 margin of wmg. On left valve one strong lateral tooth. 



Formation and locality. — Edmunds' formation, near the end or 

 Crow Neck on the northeast side of North Trescott (loc. No. 5.33.8A). 



Cotypes.—Q&L No. 58955, U.S.N.M. 



Comments. — This species by its hinge and inequality of valves is 

 distinctly within the genus Pterinea, not Adinopteria, although its 

 external appearance recalls the Devonian Actinopterias. The out- 

 line is similar to that of Pterinea dichotoma Ej-antz,^ but the beak is 



» Freeh, pi. 9, fig. 16, 



