184 



(Fig. 84.) (Pal. 



Distinguishing Characters. — Sub-circu- 

 lar or oblate outline; greater transverse 

 diameter; convex brachial valve, with 

 apex near the margin; Hat or concave 

 pedicle valve with large oval pedicle 

 groove; and Hue concentric striae, with 

 f.. ; . bs orhir,,!,,,,!,,, occasionally coarser wrinkles. 



dona. Several attached 



shells cfrom Hull). Found in the middle Moscow (Orbicu- 



loidea ) bed. al Sections 4 and 5. 



ORBICULOIDEA lodiensis. Vanuxem. 

 \. V.. Vol. IV.. p. -2-2. PI. II.) 



Distinguishing ( 'haracters — -Broadly oval-ovate outline : 

 narrower posterior end; low brachial valve, with minute 

 eccentric apex: linear pedicle groove extending 

 more than half way from apex to margin in 

 pedicle valve: concentric stria*. and faintradiat- 

 ing folds or undulations on the anterior half of 

 the shell. 



Found in the Demissa bed, at Section 5; the 

 Pleurodictyum bed, at Wanakah Cliff; the 

 Nautilus bed, in Avery's Ravine. It is rare in all. 



Measurements: <"> mm. by 5 mm. in length and width. 



Flo. 84. Orbicu- 

 loidea lodiensis. 

 Brachial valve, 

 Demissa bed, x 

 2%. (Original/) 



Genus SCHIZOBOLUS. Ulrich. 



[Ety. : Schiza, a cleft ; obobix, a genus.] 



(1886: Contributions \<> American Palaeontology, Vol. I., p. 25, PI. III. 

 Pal. X. Y.. Vol. VIII.. Pt. I., p. 87.) 



Shell oval, valves slightly unequal, margins thickened; 

 pedicle valve with a notch in the posterior margin; shell 

 substance largely corneous. Muscular callosities of pedicle 

 valve on each side of a median ridge with narrow curved 

 lateral se.-irs. brachial valve without the scars, but with 

 thickened bund just within posterior margin. 



SCHIZOBOLl s TRUNCATUB. Hall. ( Fig. 85. I ( Discina tl'UIl- 



cata. Ball. Pal. X. V., Vol. IV.. p. 2:\. Pis. I. and II.) 



Distinguishing Characters. — Abruptly rounded or trun- 

 cate posterior margin; apices of both valves near posterior 



