﻿Cephalopoda of the Cincinnati Group. 



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size, and close to ventral margin ; septa slightly convex and curving forward 

 over the contracted ventral side; chamber of habitation of medium size, 

 rapidly contracting toward anterior end. Shell from y 2 to ^ inch long, 

 and j 6 to g inch in diameter. 



Locality : Cincinnati, from middle to top of rocks. 



The small size, and gibbous character of the shell, as well as the con- 

 vexity of the septa will serve to separate this species from the preceding. 

 There is too slight a difference between G. faberi and G. cincinnatieme to 

 make two species. 



Genus 5. CYRTOCERAS, Goldf. 1832. 



De la Beche Handbuch der Geognosie. 

 Miller 1875, Gin. Quar. Jour. Sci., II, p. 131. 



-Shell curved or partly involute, sometimes with longitudinal, some- 

 times with transverse diameter the greater ; aperture contracted or not ; 

 siphuncle varying from convex to concave side. 



KEY TO SPECIES. 



Shell curved and tapering rapidly ; septa narrow. 



C. vallindighamt. \. 



Septa wide. C. faberi, 2. 



Shell ventricose. C. ventricosum, 3. 



Shell gently curved ; section elliptical; septa irregular. 



C. irregnlare, 4. 



Section sub-elliptical; chambers thin, septa concave. 



C. magista , 5. 



Section slightly elliptical ; chambers thin near the body 

 chamber. C. amoenum, 6. 



1. C. vallandighami, S. A. Miller. 1874. 



Cin. Quar. Jour. Sci., I, p. 232, fig. 23. 



C. conoidale, Wetherby, 1881. Jour. Cin. Soc. Nat. Hist., IV, p. 

 78, PI. 2, figs. 6, 6 a. 



Shell curzted and rapidly tapering ; septa short, nearly equal ; section 

 nearly circular ; surface smooth ; siphuncle small, dorsal. Length about 

 one inch — 17 to 20 septa — diameter at the ends .50 inch and .33 inch. 



Localities: Cincinnati; Columbia, Tenn.; Garrard Co., Ky.; West- 

 boro, Ohio. 



Readily recognized by the small size, curved and rapidly tapering 

 shell. There is not sufficient difference in C. conoidale to make another 

 species. 



