106 PALEONTOLOGY OF NEW-YORK. 



Stropliodoiita inequistriata. 



PLATE XVIIL 



Strophomena inequislriata .- Conrad, Jour. Acad. Nat. Sciences, Philadelphia, 1842, Vol viii, pa. 254, 



pi. 14, f.2. 

 Strophomena inegtiislriaia : Hall, Geol. Rep. 4th District, 1843, p. 290, f. 4. 

 Compare Orthit inlerttrialis : PniLLirs. Pal. Fossils, 1839, pa. Gl, pi. 25, f. 103 a, b, c. d. 

 Strophomena {Strophodonta) inequislriata : Hall, in Tenth Report on the State Cabinet, p. 142. 1857. 



Shell semioval or somewhat semicircular in outline : hinge-line extended 

 beyond the width of the shell below ; extremities acute, sometimes 

 auriculate. Rarely the sides are nearly straight below the auricu- 

 late extremities, and the basal curve rather straightened on each side 

 and produced in a subnasute extension in the middle. 



Ventral valve usually regularly convex, and often more gibbous in the 

 middle and abruptly arched towards the hinge-line, depressed-convex 

 on the disc, with the margin towards the front more abruptly curving ; 

 sometimes gently sloping towards the front and abruptly constricted 

 on the sides below the cardinal extremities, which are deflected to the 

 ventral side : the beak is small, scarcely prominent on the hinge-line. 

 Dorsal valve moderately concave, often more deeply concave ; some- 

 times moderately concave in the upper and middle part, and suddenly 

 deflected towards the front. 



Area of the ventral valve narrow-linear, extending to the extremities 

 of the hinge-line, striate vertically, with the inner margins crenulate 

 from one-half to two-thirds the length from the beak to the extremi- 



" ties : foramen none ; a slight linear elevation extends across the 

 area. Dorsal area scarcely more than half as wide as the ventral area, 

 and, in very perfect specimens, having a narrow elevated ridge cross- 

 ing it in continuation of that of the opposite valve. 



Surface of the entire shell marked by slender distant elevated striaD, 

 ■which are increased by interstitial additions ; the interspaces occupied 

 by much finer closely arranged striaj, which are scarcely visible to the 

 naked eye, and crossed by fine concentric stria3. 



