8 



CrTHEEE Tasmanjca (nov. sp.) 

 Shell minute, slightly compressed, oblong-ovate, surface 



Smooth ; there is a shallow depression near the middle. Length 



not exceeding -5 or - 75 millimetre. 



This little ostracod occurs in myriads in the Porter's Hill 



sandstones associated with Sfiirifera Darwinii, Conularia 



laevigata, and other well-known fossils of the Upper Marine 



Beds. (Up. Pal.) 



Family Astabtid2e. Genus Astabtila. (Dana.) 



Shell elongately sub-triangular, inequilateral, slightly in- 

 flated, moderately thick at the beaks, and near the Hlargins ; 

 thin in the middle ; on the surface concentrically striated or 

 lamellated ; ligament external, very long j muscular impression 

 rather large ; the anterior close to the hinge, and with a small 

 superimposed impression; pallial line entire, hinge unknown. 

 (Tryon.) 



Astabtila Robeetsii. (nov. sp.) 



Shell small, elongately oval, somewhat trigonal and equi- 

 lateral, nearly a third longer than broad ; beaks prominent, re- 

 curved, and approximate, central ; posterior, margin arched ; 

 anterior slope deeply concave about the middle ; valves' 

 regularly convex, rather compressed anteriorly ; posterior and 

 anterior muscular impression vertically oval, well-defined on 

 cast ; ventral margin gently curved ; surface ornamentation 

 unknown. 



Length, 31 millimetres ; height, 22 mil.; thickness, 1(3 mil. 



Upper Paselozoic sandstones, .New Town Palls. 



This form approaches most closely to PacJiydomus ■politus, J. 

 D. Dana, but differs in being less tumid, in having the umboes 

 more central, and in its greater comparative length : P. politus 

 being only about one-eighth longer than broad. ■ 



Family Atictjmd^;. 



Shell obliquely oval, 

 ear produced wing-like ; right valve with a byssai sinus beneath 

 the anterior ear; cartillage-pit single, oblique; hinge line 

 with one or two small cardinal teeth, and an elongated pos- 

 terior tooth, often obsolete ; posterior muscular impression 

 (adductor and pedal) large, subcentral ; anterior (pedal scar) 

 small, umbonal. (Tryon.) 



AvicuiA Tasmawica. (nov. sp.) 

 Shell small, obliquely spathulate ; bilobed coarsely striate, 

 concentrically ; hinge line scarcely as long as shell ; anterior 

 lobe small, umbonal; posterior ridge rounded and well- 

 defined ; there is a shallow wedge-shaped trough between ridge 

 1 hinge-line, the margin of which is somewhat concave ; 



Genus Avicula (Klein) Lamarck, 

 very inequivalve, eared ; the posterior 



and 



