136 PALEONTOLOGY OP KENTUCKY. 



Trematospira hirsuta. HALL. 



Plate XVI., figures 15 to 19. 



Atrypa hirsuta, Hall. Tenth Kep. on State Cabinet, p. 108 1857. 

 Trematospira hirsuta, Hall. Thirteenth Kep. on State Cab., p. 101 1860. 

 Athyris (?) chloe, Billings. Canada Journal, p. 2821860. 

 Trematospira hirsuta, Hall. Pal. N. Y., Vol. 4, pp. 274 and 2751867. 



Shell of medium size ; sub-elliptical, in very old specimens sub-circular or 

 sub-quadrate ; moderately convex when young ; increasing in convexity with 

 increasing age, and finally becoming gibbous ; sinus and fold wanting in young 

 shells, appearing at a certain age, and becoming prominent in old individuals, 

 which assume in outline the exact shape of Athyris vittata. 



Ventral valve moderately convex, with greatest convexity at the umbo, from 

 where it slopes somewhat abruptly to the cardinal margins, and gently to the 

 lateral and basal margins ; the umbo is prominent and the beak incurved ; a 

 mesial sinus is indicated in young shells ; it becomes more definite with age, 

 but remains, even in very old specimens, shallow ; this sinus is undefined in 

 its margins, which are rounded, and which coalesce with the general surface 

 of the valve, and it does never extend further back than to a little behind the 

 middle of shell. 



Dorsal valve of about equal convexity with the ventral, except in old speci- 

 mens, in which it is considerably less ; greatest convexity above the middle of 

 the valve, from where it slopes in a gentle curve to the sides and front ; umbo 

 flat, but becoming more prominent with age, and the beak strongly incurving 

 into the other valve beneath its circular foramen ; a mesial fold is only indi- 

 cated in young specimens, it becomes somewhat more prominent in older 

 shells, but never attains more than a moderate elevation, and is undefined in 

 its margins, which are rounded, and run gradually into the general surface of 

 shell. 



Surface ornamented by from thirty to forty simple, low, rounded, radiating 

 striae, which increase from beak to front in size and distance ; these radiating 

 striae are crossed by fine, concentric lines of growth, and more distant imbri- 

 cating lamellae. The surface of the specimens, as they are usually found, 

 is granulose ; but in perfectly preserved shells it is covered by minute setae or 

 spinules, the bases of which remaining, give the papillose character. The 

 entire shell structure is punctate. 



The specimen illustrated is of more than average size ; in its proportion of 

 width to length, it is more transverse than the usual form ; but at the time 

 when the drawings were made it was the only specimen at my disposal. 



Formation and Locality. Found in the rotten hornstone of the Corniferous group, in a quarry in 

 the eastern portion of the city of Louisville. Formerly very rare, but of late a good many very good 

 specimens have been found, so that my collection embraces now, at least, a dozen fair individuals. 



