305 



Distino-uishino- Characters.— R h o m - 

 boidal outline; straight upper and lower 

 marg-in ; obliquely rounded ends ; Hat- 

 tish surface: numerous strong, longi- 

 tudinal, inosculating, raised stricne, or 

 thin wrinkles with a, tendency to be- y^"^ \ 



come concentric. f — ~ : — 7^ 



Fig. 244. Entomis rhom- 



Found at "Eighteen Mile Creek, Lake hoidea Latemi aud edge 



o ' views of a left valve, x 25 



Erie Shore, X. Y." (Jones.) (after jones). 



Genus STREPULA. Jones and Hole. 



[Ety. : Dimiu. of Strepa, a stirrup, loftp-like pattern of ridges.] 

 (1886: Ann. and Mag. Nat. Hist., Ser. V., Vol. XVII., p. 403.) 



Carapace with slightly convex valves, sub-oblong with 

 rounded une(iually curved ends. Surface with narrow con- 

 centric or irregular ridges running into the slightly thickened 

 dorsal margin. The intervening furrows form l)roa(l valleys, 

 and a sub-central tubercle, or even a lobular swelling, is 

 sometimes present. The chief ridge is a free supra-marginal 

 lamina, standing outwards and downwards, and hiding the 

 real marginal edge in a side view. Edge view narrow ovate, 

 cross-barred at the sides into straight and parallel, and 

 oblique and divergent ridges. 



Strepula siGMOiDALis. Jones. (Fig. 24.').) (1890: 

 Quart. Journ. Geol. Soc, Vol. XLYL, 

 p. 11.) 



Distinguishing Ch a r a cte rs. — Acute, 

 sub-ovate outline, with straight hinge 

 line; sharp anterior and rounded pos- 

 terior end; sharp ridge bifurcating forward, the uppei- 

 branch forming a sigmoid flexure. 



Found in the "Hamilton group, at Eighteen Mile Creek, 

 Lake Erie Shore, N. Y." (Jones.) 



Strepula plantaris. Jones. (Fig. 246.) (Quart. 

 Journ. Geol. Soc, Yol. XLYL, p. 540, PI. XY.) 



Fig. 245. Strepula ,sig- 

 moidalis. Left valve, x 25 

 (after Jones). 



