165 



The fossil shells are not readily separable from T. albinella, 

 inhabiting Southern Australia, with which they agree in den- 

 tition and in the broad deep pallial inflection, the posterior 

 line of which is confluent with the pallial impression. In its 

 adult stage T. albinelloides is about the same size of ordinarily 

 full-grown examples of T. albinella ; but it is more decidedly 

 inequivalve, the right valve being markedly depressed, espe- 

 cially in the posterior half, in consequence of which greater 

 prominence is given to the small subacute umbo. The breadth 

 is proportionately less, and therefore the front dorsal slope is 

 less arched ; the post-ventral margin does not ascend so rapidly, 

 which with the straighter front dorsal margin impart a con- 

 tour sufficiently distinctive to be of specific value. The young 

 shells of each differ in the following particulars : — In T. albi- 

 nella the posterior side is narrow and more rostrated, in T. 

 albinelloides it is broader, abruptly arched, and shortly ros- 

 trated. 



The ornament is equally variable in the fossil as in the living 

 analogue. 



Tellina porrecta, spec. nov. Plate xvi., fig. 8. 



Transversely-elongated, very inequilateral, the anterior side 

 three times as long as the posterior ; narrowed and sharply 

 rounded in front, cuneiform behind ; moderately convex. The 

 ventral margin is broadly rounded at the middle and front, in- 

 curved posteriorly. Surface ornamented with fine distant con- 

 centric lira?, which are more pronounced on the posterior slope. 

 Dentition unknown. 



Dimensions. — Antero-posterior diameter, 925 ; umbo-ventral 

 diameter, 45 ; sectional diameter of one valve, one millimetre. 



Locality. — Grreen sands, Adelaide bore. 



Tellina Masoni, spec. nov. Plate xvi., figs. 6a — Gb. 



Transversely-oblong, rather convex, inequilateral, the an- 

 terior side twice as long as the posterior. Front-dorsal margin 

 elongated, hardly oblique, slightly arched ; post-dorsal margin 

 rapidly descending, straight, and narrowly truncated at the 

 extremity; ventral margin arched anteriorly and towards the 

 posterior side inconspicuously incurved. The left valve is feebly 

 concavely depressed behind the posterior carination. 



The exterior surface is ornamented by closely-set, thin, very 

 slightly elevated concentric lamella?. There are two cardinal 

 teeth in each valve, and well-developed laterals in the right. 

 Pallial sinus very large, reaching to near the anterior adductor 

 scar. 



Dimensions. — Antero-posterior diameter, 18 ; umbo-ventral 

 diameter, 11 ; sectional diameter of both valves, 6 millimetres. 



Locality. — Eare in the older beds at Muddy Creek. 



