CLINTON GROUP. 91 



This species has the general appearance of other species of the genus, but the spire scarcely 

 rises above the first volution. The oblong form of the last volution, and form of the mouth, 

 distinguish it from the preceding species, even v,-hen both appear as casts. 



Position and locality. In the lower cherty layers of the group at Medina and Lockport, N. Y. 

 484. 4. CYCLONEMA CANCELLATA '.' 



Pl. XXVIII. Fig. 5. 



This specimen is a cast in limestone, preserving only a small fragment of the shell upon its 

 base. 



The form and general character of this individual does not ditTer sufficiently from Cyclo- 

 nema cancellata to enable me to separate it. The marking of the small portion of shell preserved 

 is somewhat different, but this character is subject to variation from age and abrasion. The last 

 volution is much compressed, giving it an apparently greater extension beyond the axis than 

 would appear in the natural form of the shell. 



Fig. 5 a. The cast of the shell, which is smooth. 



Fig. 5 b. A portion of the shell from the base, enlarged. 



Position and locality. In the upper limestone of the group at Lockport, N. Y. 



485. 1. PLATYOSTOMA. 



PL. XXVIII. Fig. 4 a 6. 



Orbicular, depressed ; volutions about three, the first scarcely rising above the level of the 

 outer one ; aperture transversely oval or sub-angular. 



The cast exliibits e\idence of transverse striae, which were slightly waved upon the back of 

 the shell. 



Fig. 4 a. View looking upon the top of the spire. 



Fig. 4 b. Profile view showing the slight elevation of the spire. 



Fig. 4 c. Another specimen, view looking upon the spire. 



Fig. 4 d. View of the aperture, which is angular at the outer margin, probably from pressure. 



These two specimens are casts, with smooth rounded outlines ; but it is impossible to deter- 

 mine from them what may have been the character of the shell. 



Position and locality. This species occurs in the ferruginous sbaly sandstones of the group 

 in Kirkland and New-Hartford, Oneida county. 



486. 16. MURCHISONTA SUBULATA. 



Pl. XXVIII. Fig. 7 a, b, c, d. 

 Loxonema subulata. Conrad, Jour. Acad. Nat. Sciences, 1842, Vol. viii, pag. 273, pl. 16, fig. 14. 

 Shell subulate ; spire much elongated, and very gradually tapering ; volutions seven or 

 more in full grown shells ; height and width of volutions very nearly the same ; surface 1 



