180 PAUSONTOLOOY OF NeW-YORK. 



backwards from the suture to the mesial band, upon which they make an abrupt curve 

 forwards ; aperture rounded, extending below, with the pillar lip nearly straight. 



This is a large and beautiful species, known by its moderately ascending spire and re- 

 gularly convex or ventricose whorls, which render it readily distinguishable, in its usual 

 condition, as casts of the interior. The mesial band divides the volution almost equally, 

 producing no appreciable elevation except at the sharp marginal carina ; and where these 

 are worn down, as they sometimes are, the volutions preserve their equal convexity. 



The figure of Hisinger (6 a) corresponds very closely with our shell in form ; but the 

 mesial band is much below the centre of each volution, while ours is central. The cast 6 b 

 is too slender, and does not correspond with our species. The figure of M. de Verneuil is 

 also too slender to correspond with our species, and the mesial band produces a carina, 

 which is not a feature of the American fossil. The specimen figured by Hisinger is from 

 the more recent limestone of the Transition period ; and those in the Palaeontology of 

 Russia and the Ural Mountains, are regarded as belonging to the Upper Silurian strata. 

 The united testimony of these authors induces me to regard our species as distinct, belonging 

 to the older Silurian limestone, and never known above the Hudson-river group. In the 

 western strata of the same age, there is another more slender species, with obtusely 

 carinated volutions ; but I have never seen the outer surface of the shell. 



Fig. 1 a. A small imperfect specimen, preserving the striae and mesial band in a very perfect manner. 



Fig. 1 b. A specimen with the strias partially removed, showing the extension of the aperture below. 



Fig. 1 c. A cast, showing the form of the aperture, which is nearly entire. 



Fig. 1 d. A fragment of a larger specimen, preserving the striae and mesial band. 



Fig. 1 «. Cast of a larger specimen, the lower volutions broken off 



Position and locality. This shell is widely distributed, and is very common in the form 

 of casts. It is more abundant in the higher part of the limestone at Watertown than else- 

 where, but is occasionally found in the lower strata at Middleville. It is likewise found at 

 Trenton Falls, Herkimer, Turin, and other places. 



{State Collection ; Cabinet of the Albany Inttitute.) 



234. 11. MURCHISONIA SUBFUSIFORMIS (n. irp.). 

 Pi-. XXXIX. Figs. 2a,b. 

 Fusiform, elongated ; spire rapidly ascending ; volutions about six or more, flattened, 

 lower one large and ventricose ; aperture oval, acutely extended below ; surface? 



All the specimens discovered are casts, which preserve no remairis of external markings. 

 This species is readily distinguished from the last, by the greater obliquity of the volutions, 

 which are flattened, and never present the regularly convex outline of that species. These 

 features are preserved in the figure, and will generally be found sufficient to identify the 

 species. 



Fig 2 a. View of the back of the spire ; the apex imperfect 

 . Fig. 2 b. View, showing, imperfectly, the form of the aperture. 



