MANUAL OF THE MOLLUSCA. 



Syn.., Apioceras (Tisclier). Poterioceras (McCoy). 



Tyiie, G. pyriforme, Sby., fig. 51, and G. Boliemicuin, Bar. fig. 40. 



a 1) eoe 



Fig. 50. Eyidoceras* 



Fig. 51. Gomphoceras.\ 



pertui-e contracted in 



Shell, fusiform or globular, ^\-itli a tapering apex 

 the middle ; siplimicle moniliform, sub-central. 



Distr., 10 sp. Silui-ian — Cai-b; N. America, Europe. 



Oncoceras, Hall. 

 Etyni., oncos, a protuberance. 

 Ti/pe, 0. coustrictmn, Hall. Trenton limestone. 

 Shell, like a curved gomjihoceras ; sipbuncle external. 

 Distr,, 3 sp. Silurian, New York. 



Pheagmoceeas, Broderip. 

 Etym., 'phragmos^^ partition, and ceras, a born. 

 Type, P. ventricosum (Steininger sp.), pi. II., fig. 15. 

 Shell cm-ved, laterally compressed ; aperture contracted in the middle 

 siphuncle, ventral, radiated. Ex., P. callistoma, Bar., fig. 41. 

 Distr., 8 sp. TJ. Silm'ian — Devonian, Brit., Germany. 



* Fig. 50. Diagram of an endoceras (after Hall), a, shell-wall. h. Wall of sip- 

 huncle. c c c. Diaphragms (" embr3^o-tubes " of Hall). 



t Fig. 51. Gomphoceras pi/riforme. L. Ludlow rock, Mochtre hill, Herefordshire 

 (from Murch, Silur, syst., reduced |). s. Beaded siphuncle. 



