342 EIGHTEENTH REPORT ON THE STATE CABINET. 



GENUS PLATYOSTOMA (Conrad). 

 PLATYOSTOMA NIAGARENSIS. 



Platyostoma niagarensis : Hall, Pal. N. Y. Vol. ii, pa. 287, pi. 60, f. 1. 



Formation and locality. In the limestones of Kacine and Waukesha, 

 Wisconsin. 



GENUS STRAP AROLLUS (Montfort.) 



STRAP AROLLUS MOPSUS (n. s.). 



Shell discoid ; whorls four or more, cylindrical, very gradually enlarging, 

 the outer one sometimes a little flattened on the upper side for a part of 

 its extent : suture line strongly marked ; umbilicus very wide, and 

 showing all the volutions. Spire depressed, rising little above the surface 

 of the outer volution. The proportion of height and width is about as 

 one to three. 



The individuals measure from half an inch to seven-eighths of an inch in 

 diameter. A specimen having the latter measurement is three-tenths of 

 an inch in height. Some fragments of outer volutions indicate specimens 

 of larger size. 

 Specimens of this species, when compared with the figure of S. daphne 



(Billings), have a very similar aspect on the lower side ; but the elevation 



of the spire, as given in the description, is much too great for our species. 

 Formation and locality. In the limestone of the Niagara group, at 



Racine and Waukesha, Wisconsin. 



GENUS CYCLONEMA (Hall;. 

 CYCLONEMA? ELEVATA (n. s.). 



Shell conical ; spire elevated, gradually tapering, embracing an angle of 

 about 45 deg. Volutions rounded, ventricose, about five ; gradually 

 enlarging to the aperture, which has been nearly circular. 

 The cast from which the species is described, possesses evidence of 



revolving striae, without indications of a central band. 



Height nine-tenths of an inch ; width six-tenths of an inch. 



Formation and locality. In limestone of the Niagara group, at Racine, 



Wisconsin. 



GENUS HOLOPEA (Hall). 



HOLOPEA HARMONIA? 



Holopea harmonia : Billings, New Species of Silurian Fossils, pa. 158, f. 142. 1862. 



There are several specimens in the collection, so nearly corresponding 



with the figure given by Mr. Billings, that I must regard them as the 



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