124 



Lithodomus, sp. Indet. 



Casts and crypts of a Lithodomus in tlie coral Plesiastrcea 

 Yincenti occurring at Hallett's Cove indicate a short tumid 

 •shell with broad incurved beaks, the anterior end slightly con- 

 vex, the posterior obliquely obtuse. 



Length, 21; breadth, 10; thickness through both valves, 11 

 millimetres. 



GrE:NUS MYTiLrs. 



Sliell cylindrical tumid. 3£. sp. 



Shell subquadrangular. M. subMenheanus. 



Mytilus, sp. Indet. 

 An imperfect specimen of a cylindrical tumid mussel, finel}'- 

 longitudinally striated on the steep ventral slope, has been 

 obtained from the glauconitic limestone at Blanche Point, 

 Aldiuga Bay. Length 47, width 15 millimetres. 



Mytilus subMenkeanus, spec nov. 



A complete diagnosis is impossible from the fragmentary 

 state of the specimens, which, however, indicate a species of 

 the general form of the recent M. Ilenkeanus, but with fewer 

 and stouter longitudinal ribs. 



Locality. — Hallet's Cove, on the horizon of the oyster banks 

 ^t Aldinga Bay. 



Septifer fenestratus, sijec. nov. PI. ix., fig. 1. 



Shell elongate-triangular, very inequilateral, equivalve ; 

 umbos almost marginal, subacute, curved ; anterior side nearly 

 straight, slightly outwardly convex about the middle, rising 

 abruptly to the elevated rounded umbonal ridge ; dorsal line 

 straight ; post-dorsal area depressed, its margin making an 

 obtuse angle (about 120°) with the dorsal line ; ventral margin 

 attenuated, rounded ; byssal sinus inconspicuous. Surface 

 ornamented with numerous divaricate subacute ribs, the inter- 

 spaces shallow, concave, broader than the radial ribs, latticed 

 by stoutish raised lines ; also by distant imbricating folds of 

 growth. Hinge thickened anteriorily with a small umbonal 

 shelf (umbonal cavity is filled up at the senile stage of growth); 

 ligamental groove linear, slightly obliquely extending poster- 

 iorly ; the whole inner margin of the valves crenulated, the 

 crenulations on the hinge line becoming denticulate, and three 

 •or four beneath the umbo are much larger than the rest. 



Diinensioiis- — Length of hinge-line, 9"5 ; antero-dorsal to 

 post-ventral margins, 16 ; thickness through both valves, 8 

 millimetres. Kn unusually large specimen has the first two 

 dimensions respectively 28 and 44 millimetres. 



Localities. — Muddy Creek; Corio Bay; Schnapper Point, 

 Hobson's Bay, Victoria {R. T.). 



