P. E. Raymond — Fauna of the Cliazy Limestone. 371 



Orthidium lamellosa sp. nov. 



Ventral valve strongly convex, the area high and curved 

 backward. Delthyrium narrow and open. Along the middle 

 of the valve is a narrow and shallow depression in which there 

 is one plication. The outline of the shell is subquadrate. The 

 greatest length is at the hinge and the cardinal extremities are 

 slightly alate. 



The dorsal valve has a narrow median sinus, which extends 

 from the beak to the front and usually contains 2 plications. 

 There are commonly about 20 sharp plications, which are 

 crossed by strong concentric lamellae of growth. 



An average specimen is 3 mm long and 5'5 mm wide. 



Locality. — Yalcour Island, Chazy, and Crown Point, New 

 York. The types are in the Yale University Museum. 



PELECYPODA. 



Ctenodouta j^er acuta sp. nov. 



Shell small, longer than high, the beak about one-third the 

 length from the posterior margin. Front rather drawn out, as 

 in Ctenodouta nasuta Hall. The greatest convexity is at the 

 umbo, the posterior slope very gradual. Both slopes to the 

 hinge abrupt, but that to the basal margin gentle. One speci- 

 men is 12 mm long and 9 mm high. This species may be distin- 

 guished from the succeeding one by its more depressed valves 

 and by the prolongation of the -anterior margin into a some- 

 what nasute extension. 



Locality. — Found in some numbers in the trilobite layers at 

 Sloop Bay, Yalcour Island, and in the middle of the Crown 

 Point section. The type is in the writer's collection. 



Ctenodouta limbata sp. nov. 



Outline nearly circular, the beak back of the middle. 

 Greatest convexity near the middle of the valve ; all slopes 

 steep. The cast shows a few faint lines of growth. 



Length of largest specimen 10 mm ; height 10 mm . A smaller 

 one measures 8 x 8 mm . 



Loccdity. — All the specimens are from the trilobite layers, 

 Sloop Bay, Yalcour Island. The types are in the Yale Uni- 

 versity Museum. 



Ctenodouta dubiaformis sp. nov. 



Shell small, moderately convex, beak subcentral. Greatest 

 convexity on the umbo, the. slope from it to the base nearly 

 flat. Basal margin nearly straight. Anterior end nasute and 



