316 
round foramen, rendered complete by a distinct deltidium ; 
hinge area small, triangular sharply defined; interior with 
diverging shelly spires. (Silur-Trias.) 
Retzia mima, Salter, M.S. Tasmania West. 
Class Prtecypopa (Lamellibranchiata or Conchifera.) 
Cyrtodonta Billings (Cypricardites, Conrad.) 
Bigsby’s Thesaurus. Sil 1868. Hth. Cat. p. 23. Austr. 
Fossils. 
Shell ventricose, suborbicular or broad ovate in outline, 
with an external flattened ligamental area; cardinal teeth 
four to five; short oblique; lateral teeth two or more oblique ; 
muscular impressions two (anterior one single ?) ; pallial line 
simple. (Tryon.) d 
. auriculata. Salter (MLS.) Tasmania, West. 
. compressa. 
. distorta. 
. gibbulosa. 
. inflata. 
C 
C 
C 
C. obliquata. 
C 
C 
E 
Qa 
. penguis. 
. reversa. 
unema. Salter. 
Bigby’s Thes. Sil. 1868; Hth. Cat. Austr. Fossils, 
p. 24. 
E. emula. Salter, M.S. Tasmania West. 
Straparollus, Montfort, 1816. 
EHuomphalus Sowb.,; Helicotoma, Salter. 
Bigsby’s Thes. Sil, p. 868; Eth. Cat. Austr. 
Fossils, p. 24. Tryon ii., p. 218. 
Shell depressed; Whorls, angular or carinated ; aperture, 
sub-quadrangular ; umbilicus wide, conical ; operculum 
shelly, multi-spiral. (Tryon.) Lower Silurian to Trias. 
United States, Europe, Australia. 
S. emula. Salter (M.S.) Tasmania, West. 
S. (Helicotoma). Milligani ,, 
S pusilla cr rs 
Raphistoma. Hall, 1847. 
Bigsby’s Thes. Sil., 1868. Eth. Cat. Austr. 
Fossils, p. 25. Tryon IL., p. 219. 
Shell, lenticular, or orbicular; whorls, flattened, with a 
carination above ; umbilicus, moderate; outer lip, with slight 
sinus at the keel. (Tryon.) 
RR. eterna. Salter (M.S.) Tasmania, West. 
R. (Holopaea) 
Scalites. (Conrad M.S.) Emmons, 1842. 
Bigsby’s Thes. Sil.. 1868; Eth. Cat. Austr. 
Fossils, p. 25. Tryon ii., p. 223. 
