432 REPORT ON THE STATE CABINET. 



the rocks of Wisconsin and Illinois ; numerous specimens presenting 

 differences of outline, which are easily recognizable. The accompany- 

 ing outline figures are, 1, copied from the figure given by M'Chesnet 

 of Anibony cilia neglecta ; and 1,iv(mx AmpMcoelia leidyi. It may require 

 farther comparison, with larger collections, to demonstrate the identity 

 or difference of these forms. 



Plattostoma niagarensis, Hall. 



(Page 390.) 



Platyceras campanulatum, W. & M., seems to be only one of the many 

 phases assumed by the above species, in its wide geographical distri- 

 bution. 



PORCELLIA SENEX, WiNCH. AND MaB. 



" Shell small, consisting of one and a half or two very rapidly enlarging, 

 detached whorls, which are somewhat oblique in the young shell, 

 but afterwards continue very nearly in one plane. Toward the 

 aperture the shell is flattened and subnodulous on the dorsum." 



The specimen is a cast of the interior of a Platyceras, closely allied 

 to P. niagarensis ; and the spire is oblique throughout its entire extent, 

 the two sides of the shell being nowhere symmetrical. There are a few 

 undulations on the back, from inequalities of growth at the aperture, 

 which has been deeply sinuate ; but there is no evidence of the narrow 

 carina on the dorsum, or slit at the aperture, characteristic of Porcellia. 



Pleurotomaria halei. Hall. 



(Page 392.) 



Notwithstanding the fact that Prof. Winchell has identified P. axion 

 as the species he referred to P. halei, the specimens which he sent to me 

 under the latter name are not of that species, but of Pleurotomaria 

 {Trochonema ?) pauper. In Prof. Marct's collection there are numerous 

 specimens of the latter species, and one fine cast of P. halei ; but neither 

 in this collection, nor in that sent by Prof Winchell, is there any speci- 

 men of P. axion. 



