265 



Genus PAEACYCLAS. Hall. 



[Ety. : Para, allied to; cydas, a genus.] 

 (1843: Gcol. Surv. N. Y., Report, 4th Dist., p. ITL) 



Shells with equal, nearly e(inilateral, valves, sub-orbiciilar 

 or broadly sub-elliptical. The anterior end is regularly 

 rounded, the posterior end rounded or sub-truncate. Small 

 low beaks, short hing*e line, concentric striae, and often con- 

 centric ridges, further characterize this genus. 



Paracyclas LiRATA. (Courad.) (Fig. 18G.) 

 Vol. v.. Pt. I., p. 441, Pis. LXXIL, 

 XCV.) 



Distinguishing diameters. — Nearly 

 circular outline ; medium size; strong 

 concentric ridges. 



Found in the hard layer of Mar- 

 cellus age, ten feet above the base, 

 at the northern end of Atliol Springs 

 Cliff (very rare). 



Pal. X. Y., 



Fig. 186. Parari/clafi lirata 

 (from Hall). 



Gems TELLINOPSIS. Hall. 



[Ety. : Resembling a Tellina.] 

 (1880: Preliminary notice Lamellibrancbiata, 2, p. 80.) 



Shells with equal, nearly equilateral valves, sub-elliptical 

 in outline. The anterior end is rounded and the posterior 

 end sub-truncate or emarginate. Small beaks, gently curving 

 cardinal line, prominent umbonal slopes, small external 

 ligament, concentric stri;p, and radiating striji^ (sometimes 

 obsolete), are other characteristic features. 



Tellixopsis sub-emarginata. (Conrad.) (Fig. 187.) 

 (Pal. N. Y., Vol. v., Pt. I., p. 4G4, PI. LXXYl.) 



DistinguisliingCIiaracters. — Sub-emarginate posterior end ; 

 large roimded anterior end ; oblique depression extending 

 from the beak to the posterior margin, or below; flattened 

 space, limited on each side by a ridge and extending from 

 the beak to the antero-basal margin; fine concentric and 

 fine radiating strift^. 



