TF. H. HucUedon — Fossil Shells from South Australia. 341 



ligament. Pallial margin curved. Umbones moderate (outer shell 

 layer removed by erosion at the beak). Surface of shell nearly 

 smooth, with flat concentric borders at rare intervals, crossed by very 

 fine irregular radiating striae. 



Cast. — Anterior muscular impression better marked than posterior. 

 Pallial sinus narrow. 



Cyprina ? species. PI. XI. Figs, la, 7b. 



Width and length equal ; posterior area but slightly larger, very 

 thick towards the umbones, and compressed in the pallial area, the 

 margin of which is raucb rounded. Hinge-area sloping sharply on 

 both sides. Lunule wide and deep, ligamental excavation wide and 

 short. Shell substance very thick towards the umbones, tapering 

 towards the lower border (partly due to unequal corrosion). Shell 

 probably without ornament beyond concentric bands at intervals. 



Cast much corroded, no trace of pallial sinus visible. 



MoDiOLA LiNGULOiDES, sp. nov. PI. XL Figs. Qa, Gb. 



There are two rather well-preserved specimens of Mocliola, which 

 appear to belong to the same species, though there is a considerable 

 diflference in appearance at first sight, owing to different portions of 

 shell and cast being preserved. 



The smaller one, which is in the best condition of the two, 

 measures 30 mm. from the umbones to the lower border. The shell 

 is linguloid in outline, extremely inflated, anterior margin nearly 

 straight, anterior area very full and without any inflection. Umbones 

 subcentral, tumid and strongly curved anteriorly. Cardinal area 

 well developed and projecting slightly beyond the posterior margin, 

 which falls away nearly straight towards the lower border. Shell 

 widely grooved concentrically, the grooves or flutings being cut 

 deepest on the anterior side. Interior shell layer nacreous. 



It is not often that fossil Modiolas display such well-preserved 

 umbos. On the whole, the condition of the shell scarcely gives one 

 the notion of a very high antiquity. 



Gekvillia angusta, sp. nov. PI. XI. Fig. 5. 



Two double valves of what appears to be a species of GerviUia 

 partly cast, and partly shell, though no certain traces of auricles can 

 be made out. The valves are narrow, and appear to have been dis- 

 posed in concentric imbrications of considerable breadth. The shell 

 substance has been in great part removed, being now chiefly repre- 

 sented by ferruginous flakes on a fine-grained calciferous grit. The 

 shell was lanceolate, hardly at all curved, with a median ridge 

 extending in the direction of the lower area, which was much com- 

 pressed. 



AvicuLA ORBICULARIS, sp. nov. PI. XI. Fig. 10. 



There are two specimens of a species of Avicula with both valves 

 in apposition, though more or less slipped out of place. The shell 

 having been thin, they exist partly as casts and partly representing 

 the original shell substance. 



Shell orbicular, length and width almost equal, very nearly equi- 



