CEPHALOPODA. 193 
have resembled Gonioceras, and the external tube to be a simple 
cavity, formed by the approximation of the lateral angles. 
Discosorus (conoideus) Hall, 1852. Pal. New York. This 
fossil appears to be a siphuncle similar to those figured by Dr. 
Bigsby in 1824 (Geol. Trs. I., Pl. 30, f. 6), and which have been 
correctly referred to the orthocerata by Quenstedt. 
GoMPHOCERAS, J. Sby. 1839. 
Etymology, gomphos, a club; and ceras, a horn. 
Synonyms, Apioceras (Fischer). Poterioceras (McCoy). 
Type, G. pyriforme, Sby., Fig. 58, and G. Bohemicum, Par. 
Fig, 47, 
= 
Fig. 57. Engoceras.* Fig. 58. Gomphoceras.t 
Shell, fusiform or globular, with a tapering apex; aperture 
contracted in the middle; siphuncle moniliform, sub-centvral. 
Distribution, 27 species. Lower Silurian—Carb. North 
America, Europe, Brit. Barrande figures 70 species in Vol. II. 
of his ‘‘ Systéme Silurien,” 1865, nearly all of which are believed 
to be new. 
ONcOCERAS, Hall. 
Etymology, oncos, a protuberance. 
Type, O. constrictum, Hall. Trenton limestone. 
* Fig. 57. Diagram of an endoceras (after Hall). a, shell-wall; 6, wall of siphuncle’ 
tcc, diaphragms (‘fembryo-tubes’’ of Hall). 
+ Fig. 58. Gomphoceras pyriforme. L. Ludlow rock, Mocktree Hill, Herefordshire, 
{From Murchison’s Silurian Syst. reduced 3.) s, beaded siphuncle. 
K 
