:}()9 

 Genus CTEXOBOLBINA. Ulrich. 



[Ety. : Ktenos, comb; bolbos, bulb.] 

 (1890: Journ. Cin. Soc. Nat. Hist., Vol. XIII., p. 108.) 



Carapace small, elongate, sub-oval, strongly convex. The 

 posterior two-fifths more or less decidedly bulbous, or 

 sub-globulai", and separated from the remainder by a deep 

 narrow sulcus, extending in a gentle curve from the dorsal 

 margin more than half the distance aci-oss the valves 

 towards the posterio-ventral border. The anterior three- 

 fifths, often with another oblique, but less impressed, sulcus. 

 Valves equal, the dorsal margin straight, hingement simple, 

 the ventral edge thick, and the true contact margins gen- 

 erally with a row of small spines on each side; in a lateral 

 view both are concealed by a "frill'" or flattened border, 

 usually mistaken for the true contact edges. Surface gen- 

 erally granulose. 



Ctexobolbina MINIMA. UlHch. (Fig. 252.) (Journ. Cin. 

 Soc. Nat. Hist., Vol. XIIL, p. 188, PI. XV.) 



Distinguishing Characters. — Small size; strong oblique 

 sulcus ; ventral spine posteriorly ; dorsal 

 spine wanting, or represented by a \ \/ 



minnte tubercle on the posterior side of 



^ Fig. 252. Ctenobnlbina 



the sulcus; smooth, moderatelv convex, mnumo. Aright vaive, x 



' ' - '20 (after Ulrich). 



surface. 



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

 near Buffalo, N. Y.'' (Ulrich, type. ) 



Genus MOOREA. Joxes and Kikby. 



[Ety. : Proper name.] 

 (1869: Ann. and Mag. Nat. Hist., Ser. IV., Vol. III., p. 22.5.) 



Carapace with simple, thick, flattened valves, longer on 

 the dorsal than the ventral mai'gin, without any sub-central 

 pit, and ornamented with narrow, rounded ridges, follow- 

 ing more or less closely and completely the marginal con- 

 tour. 



