108 [Senate 



angle. Surface marked by undulations parallel to the margins of the aperture, 

 and apparently by finer striae in the same direction : surface characters not 

 fully known. 



Geological formation and locality. In the same strata with Goniatites oweni 

 and G. rotatorius : Rockford, Indiana. 



PLEUROTOMARIA VADOSA ( n. s.). 

 Shell depressed subcorneal or ovoid : volutions about four, rapidly expanding; 

 the last one marked by several revolving ridges, and a more prominent one along 

 the back. In the cast the upper volutions are regularly rounded on the exterior, 

 and the last one subangular from the prominence of the carina and the charac- 

 ters of the exterior shell : width from half to three-fourths of an inch, with 

 equal height. 

 Geological formation and locality. The same as the preceding. 



PLEUROTOMARIA RUGULATA ( n.s.). 



Shell depressed conical or ovoid : volutions four or five, very rapidly expanding, 

 the body volution forming almost the entire bulk of the shell; volutions rounded 

 exteriorly, the last one showing a carination (upon the cast) towards the aper- 

 ture. Aperture broadly expanded, and the lip somewhat reflexed on the lower 

 side. Surface marked near the aperture by strong folds parallel to the margin, 

 which are preserved in the cast; while regular and sharply elevated striae, pa- 

 rallel to the lines of growth, which are distant about twice the diameter, mark 

 the surface of the shell : also some extremely faint revolving lines are visible. 

 This shell has the form of the preceding, but is larger, with the last volution 



more ventricose; and the sharp vertical striae, with or without faint revolving 



ones, are characters not observed in the preceding. 



Geological formation and locality. In the Goniatite limestone, associated with 



G. expansus, Discites, Orthoceras, etc., at Schoharie. N.Y. 



PLEUROTOMARIA.? MITIGATii (n.s.). 

 Shell smaU, ovate : volutions four or five, gradually enlarging above; the body 



volution becoming ventricose, and consituting much the larger part of the bulk 



of the shell. Aperture ovate. 



The back of the volutions in the cast are marked by an obscure revolving band, 

 but the surface markings are otherwise unknown. 



The specimens are casts, and consequently their reference to Pleurotomaria is 

 with hesitation. 



Geological formation and locality. In the Goniatite limestone, at Rockford, 

 Indiana. 



MURCHISONIA (PLEUROTOMARIA.?) LIMITARIS (n.s.). 



Shell teretely conical : volutions five, six or more, rapidly ascending and in- 

 ci-easing moderately in size, angular on the periphery in the cast, flattened on 

 the upper side and rounded below; the last one flattened on the back towards 

 the aperture, which is somewhat rounded. Surface characters not fully known; 

 the lower side of the last volution marked by strong revolving striae below th 

 central revolving band. 

 Geological formation and locality. In the same strata, associated with the 



preceding. 



