137 



Dimensions. — Length, 45; width, 42 ; thickness through 

 valves, 33 millimetres. 



Localities. — Ti/pe, Table Cape (i?. 21. Johnston!). Var., com- 

 mon at Muddj Creek ; Adelaide bore. 



Pectunculus laticostatus, Quoyand Gaimard{?). 



Beferences. — Yoy. de 1' Astrolabe, t. 77, figs. 1-6, vol. iii., 

 p. 466, McCo}^ Prod. Pal., A^ictoria, Dec. ii., t. xix., figs. 10-14. 



Localities. — Bird Eock, G-eelong ; of small size, Schnapper 

 Point {McCoy). 



This identification of the fossil and the living species has 

 been disputed by Mr. E. M. Johnston. The material at my 

 command is not sufficient to permit me to express an opinion, 

 though I have little hesitation in accepting Prof. McCoy's de- 

 termination in respect to the fossils represented by fig. 10. 



Pectunculus McGoyii, E. M. Johnston. 



Beference. — Proc. Eoy. Soc, Tasm., for 1884, p. 199. 



The characteristic shell of Table Cape, previously referred 

 to the living species, P. laticostatus, is regarded by Mr. John- 

 ston as specifically distinct, with the following differential 

 characters: — Eibs, 29 (not 39), less solid, longer than broad, 

 more convex towards the margin; hinge teeth, 10. 



A thin, sub-orbicular, narrowed at the hinge, depressed 

 shell, never exceeding 30 millimetres diameter, very abundant 

 at Muddy Creek, is tentatively included under P. McCoyii. 



Localities. — Table Cape, Tasmania ; Cape Schank, Victoria 

 {B. M. Johnston!); Muddy Creek and Schnapper Point {B.T.). 



Pectunculus subtrigonalis, spec. nov. PI. xi., figs. 6a — 6&. 



Shell solid, somewhat sub-trigonal, sub-equilateral, oblique, 

 slightly produced posteriorly, moderately convex, radiately 

 ribbed ; ribs about 29, rounded, separated by flat narrower in- 

 terspaces, the whole surface crossed by regular, sub-distant, 

 subimbricating lamellae, and a few folds of growth ; umbones 

 small, approximate ; hinge line very short, ligamental area 

 small ; cardinal teeth eight in front and seven behind the 

 edentulous centre ; internal margin of valves strongly crenate. 



This species is conspicuous by its narrow hinge line, the 

 valves attaining the greatest transverse diameter at about 

 four-sevenths the distance from the umbo to the front. 



Dimensions. — Length, 32 ; width, 31 ; thickness through both 

 valves, 19 millimetres. 



Localities. — Common in the calciferous sandrock of the 

 Eiver Murray cliffs near Morgan {B.T.) ; rare Muddy Creek 

 (J", Dennant !). 



