CEPHALOPODA— AMMONOIDEA. 135 



Small, slender, scarcely tapering; septa somewhat oblique. 

 Marcellus of New York. 



196. B. arkonensis Whiteaves. Devonic. 

 Small, gently tapering, of circular section ; septa concave ; simi- 

 lar to, but smaller than, preceding. 



Hamilton of Ontario. 



197. B. gracilior Clarke. (Fig. 1387, a.) Devonic. 

 Large, of subcircular section, nearly cylindrical ; adult with 



obscure, low, transversely oblique wrinkles ; living chamber often 

 with constrictions. 



Naples shales and limestones of New York and Michigan. 



198. B. aciculum (Hall). (Fig. 1387, &.) Devonic. 

 Slender, rapidly tapering to point, commonly compressed ; length 



three inches or over, with aperture 7 mm. in compressed specimens. 

 Naples shales and limestones of New York. 



Agoniatitida {Agoniatitidcc). 



LXXV. Agoniatites Meek. 



Round whorled in young, becoming flattened ventrally in later 

 stages and laterally compressed, more or less close coiled ; aper- 

 ture with deep, hyponomic sinus ; adult sutures comparatively 

 simple with broad lateral and deep ventral lobes separated by 

 narrow saddles. Devonic. 



199. A. expansus (Vanuxem). (Fig. 1388.) Devonic. 

 Large (a foot or more in diameter) ; half grown shell with ribs 



and flat venter bounded by lateral carinae; adult venter scarcely 

 flattened, with rounded lateral angles; sides flat. 



Agoniatite limestone of Marcellus in New York, Maryland, etc. 



LXXVL ToRNOCERAS Hyatt. 



Similar to preceding, but whorls compressed and annular lobes 

 present. Devonic. 



200. T. uniangulare (Conrad). (Fig. 1389, c?, ^.) Devonic. 

 Umbilicus closed; venter rounded; surface smooth except for 



growth lines. 



