317 
Shell, turriculated; whorls, flattened above, angulated at 
the shoulder and convex below; outer lip, sinuous; 
umbilicus, none, or very small. Silurian. United States, 
Australia. (Tryon.) 
S..(Holopea). Mumia. Salter (M.S.) Tasmania, West: 
S. Australis, ditto bs 
CLASS GASTEROPODA. 
Bellerophon, De Montfort, 1808. 
Microceras. Hall; Bigsby’s Thes. Sil., 1868, 
Hth. Cat. Aust. Fossils, p. 24. Tryon IL., p 322. 
Shell, symmetrically convoluted, globular, or discoidal; 
strong, few-whorled; whorls often sculptured; dorsally keeled ; 
aperture, sinuated, and deeply notched on the dorsal side. 
Cambrian to Carboniferous; North America, Europe, 
Australia, India. (Tryon.) 
B. pugnus. Salter (M.S.) Tasmania, West. 
Trochonema. Salter, 1859. 
Trochonemopsis, Meek; Bigsby’s Thes. Sil., 1869. 
Eth. Cat. Aust. Fossils, p. 25. Tryon IL, p. 309. 
Shell, delphinula-like, with wide umbilicus. (Tryon.) Sil. 
Europe, America, Australasia. 
Hormotoma. Falter, 1859. 
Bigsby’s Thes. Sil., 1863. Eth. Cat. Aust. Fossils, p. 25. 
: Lower Sil. 
H. nerinzwa. Salter (M.S.) ‘Tasmania, West. 
Murchisonia, D Archiac and De Vernewil, 1841. 
Bigsby’s Thes. Sil., 1868. Eth. Cat. Aust. Fossils, p. 25- 
Shell, elongated ; many whorled; whorls, variously sculp- 
tured, and zoned, like Pleurotomaria; aperture, slightly 
channeled in front; outer lip, deeply notched. I. Silurian to 
Permian ; North America, Europe, Australasia. (Tryon.) 
M. Franklin. Salter (M.S.) Gordon Limestone, Tas. 
M. mimetica. i“ . £ sa 
Tellinomya, Hall, 1847. 
Ctenodonta, Salter, 1851. 
Tryon il., p. 260; Bigsby’s Thes. Sil. 1868, p. 144. 
Eth. Cat. Austr. Foss. p. 25. 
Shell elongately oval, sub equilateral, smooth, or finely 
concentrically striate; valves moderately convex; hinge re- 
presented by two diverging comb-like denticulated margins, 
without a special hinge area between them and the beak, and 
below the latter, not interrupted by a pit; ligament apparently 
external, posterior to the beak. (Tryon.) 
