NIAGARA FALLS AND VICINITY 



201 



Genus trematospira Hall 



[Ety. : rp7j[ia, foramen; o-mTp a, spire] 



(1859. N. Y. state mus. nat. hist. 12th an. rep't, p. 27; 1893. Pal. 

 N. Y. v. 8, pt 2, p. 124) 



Shells transverse, with subequally convex valves; surface radially 

 plicate; hinge line straight, cardinal extremities abruptly rounded; 

 anterior margin sinuate. Pedicle valve with a median sinus and an 

 incurved beak, truncated by a circular foramen. Delthyrium cov- 

 ered by two short incurved plates, which are usually closely an- 

 kylosed, and appear continuous, with a narrow, flattened area on 

 either side; lower half of the delthyrium open, for the reception of 

 the beak of the brachial valve. Teeth prominent, arising from the 

 bottom of the valve ; above the hinge line they curve backward and 

 toward each other, thus making a very firm articulation. Muscular 

 area well defined. Brachial valve with median fold, and minute 

 beak. Hinge plate greatly elevated, with a small chilidium resting 

 against it ; upper face of plate deeply divided by median longitudinal 

 groove, and more faintly by transverse groove. Dental sockets 

 small and deep, crura broad, thin and comparatively short. Brachi- 

 dium of two spiral cones set base to base, as in S p i r i f e r . 



Trematospira camirra Hall (Fig. 

 122). Atrypa camura Hall (1852. 

 Pal N. Y. 2 :273, pi. 56) 



Distinguishing characters. Small; 

 subrhomboidal to transversely elon- 

 gate; nearly equally convex valves. 

 Small, acute, projecting and slightly in- 

 curved beak of pedicle valve, showing 

 in young shells the ankylosed deltidial plates; strong, distant, simple 

 subangular plications, one or two fine ones in the center; fine, 

 thread-like concentric striae and coarse lamellae. 



Found in the Bryozoa beds of the Rochester shale at Niagara, 

 rather common. Also at Lockport and elsewhere (Hall). 



Genus whztfieldella Hall & Clarke 



[Ety.: proper name] 



(1893. Pal. N. Y. v. 8, pt 2, p. 58) 



Shells usually of small size; valves subequally convex, ovate or 

 elongate in outline; beak of pedicle valve not high or greatly in- 





Fig. 122 Trematospira camura 



