90 



MA^'UAL OF THE MOLLUSCA. 



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



Type, G. pyiilbrme, Sby., fig. 51, aud G. Bohemicum, Bar. fig. 40. 



a 6 Goe 



Fig-. 50. Efidoceras.* Fig. 51. GomphocerasA 



Shell, fusiform or globular, with a tapering apex ; aperture contra/cted in 

 the middle ; siphuncle moniliform, sub-central. 



Distr.^ 10 sp. Silm'ian — Cai-b ; N. America, Europe. 



Oncoceras, Hall. 



Etym., oncos, a protuberance. 

 Type, 0. constrictum, HaU. Trenton limestone. 

 Shell, lil^e a curved gomj}hoceras ; siphuncle external. 

 Dktr., 3 sp, Silurian, New York. 



Pheagmoceras, Broderip. 

 Etym., pkragmos^Q. partition, and ceras, a horn. 

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

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

 siphuncle, ventral, radiated. Ex., P. callistoma, Bai-., fig. 41. 

 Bi&tr^ 8 sp. U. Silm-ian — Devonian, Brit., Germany. 



* Fig. 50. Diagram of an endoceras (after Hall), a, shell-walL 6. Wall of sip- 

 huncle. c c c. Diaphragms (" embryo-tubes" of Hall). 



t Fig. 51. Gomphoceras pyriforme. L. Ludlow rock, Mochtre hill, Herefordshire 

 (from Murch, Silur, syst., reduced |). «. Beaded siphimcle. 



i I 



