230 Annals of the Carnegie Museum. 



This species differs fron Petrocrania ulrichi (Hall and Clarke) in 

 having the apex nearly marginal instead of sub-central, in having the 

 anterior adductors further back and nearer together, and in the shape 

 of the vascular markings. 



Locality. — This species is common at a single locality on the east 

 side of Valcour Island, and rare at Sloop Island, and at Chazy, New 

 York. 



Order Protremata Beecher. 



Family STROPHOMENID.'E King. 



Genus Lept.^na Dalman. 



14. Leptaena incrassata Hall. 



(Plate XXXIV, figures 32-37-) 

 Leptana incrassata Hall, 1847. Paleontology New York, Vol. I, p. 19, PI. 4 bis, 



figs. 2a-2C. 

 LeptcEna fasciala Hall, 1847. Ibidem, figs. Z'l' 3^- Non 3c. 



Leplcena incrassata Rogers, 1858. Geology Pennsylvania, pt. 2, p. 817, fig. 519. 

 Stropiwmena fasciata Hall, 1858. Twelfth Annual Report New York State Cabinet 



Natural History, p. 70. 

 Strophomena incrassata Billings, 1859. Canadian Naturalist and Geologist, 



Vol. IV, p. 443. 

 Rafinesquina fasciata Hall and Clarke, 1892. Paleontology New York, Vol. 



VIII, pt. I, p. 283. 

 LeptcBna incrassata Winchell and Schuchert, 1893. Paleontology Minnesota, 



Vol. Ill, pt. I, p. 410. 



After comparison of a full series of specimens with the figures of 

 LeptcBna incrassata and L. fasciata in Volume I of the "Paleontology 

 of New York" it becomes evident that both of Hall's species are founded 

 on the same type of shell. The figure 3c in the original illustrations 

 of LeptcBna fasciata was made from a specimen collected at Galway, 

 Saratoga County, New York. This shell is very different from the ones 

 shown in the other figures, and as the Chazy formation does not occur 

 at Galway, it is very probable that this shell did not come from that 

 formation. 



This shell is rather common in the upper part of the Chazy on Val- 

 cour Island, and is easily recognized by its transverse outline and the 

 abrupt deflection of the front. In young shells the outline is nearly 

 circular, the brachial valve is nearly flat, and the front is not deflected. 

 Hall probably had one of these young shells in hand when describing 

 Leptccna fasciata. Leplcena incrassata is much like L. charJottcc Win- 



