

arus 



Fossils from Australia. 153 



ductus fragilis. — Subquadrate, with front angles rounded, 

 rather broader than long, hinge line straight, nearly of the breadth of 

 the shell, front straight, upper valve very convex, irregularly longitudi- 

 nally striated, with some concentric plications, sometimes with occa- 

 sional rudiments of spines, front and sides rather abruptly reflexed ; 

 beak small, projecting but little below the hinge line, and the apex 

 not much inflexed. — Length of hinge line 1 J inches ; depth of con- 

 cavity below, over half an inch. — This species is very unlike the bra- 

 in its less prominent beak and longer hinge line. It is near 

 the rugosus, but is much thicker and more convex above. — lllawarra. 



15. Solen (Solecurtus ?) ellipticus. — Shell very slightly convex, very 

 regularly elliptical, with no trace o( a beak, breadth little less than 

 half the length, anterior part rather more than one-third the whole 

 length ; smooth with fine scarcely apparent concentric strise, supero- 

 anterior margin slightly depressed, and perhaps two or three faint radi- 

 ations from the hinge over the lateral surface (apparent in the cast of 

 the under surface of the valve, but not of the upper) ; cast of the hinge 

 showing no teeth though apparently perfect. — Length 1*4 inches ; 



hei gh tVit L.— lllawarra. 



16. Solen (Solecurtus ?) planulatus. — Shell flat except a slight 

 bending over the postero-dorsal portion ; no beak, elliptical in outline 

 with the inferior and dorsal margins straight, and the anterior and pos- 

 terior extremities of equal breadth ; breadth more than half the length ; 

 surface smooth with some faint concentric undulations and lines of 

 growth, apparent especially near inferior margin ; no palleal or mus- 

 cular impressions visible.— Length U inch ; height T 4 A L.— Har- 

 per's Hill. 



17. Pholadomya undata. — Nearly or quite equivalve, oblong trans- 

 verse, subelliptical ; beak projecting but little ; thinning to an acute edge 

 ln front, prolonged and narrowing somewhat behind ; sides flattened, 

 posterior surface from the beak to the posterior angle obliquely trun- 

 cate and exteriorly subcarinate ; cardinal area linear, circumscribed ; 

 surface with a few irregular obsolescent longitudinal plicce or undula- 

 t'ons, smooth, crossed, especially below, by faint radiations.— Length 

 h\ inches; height Jfo L ; thickness ^L; distance of summit of 

 £eak from anterior margin T %\ L ; apical angle 138°; projection of 

 »eak above cardinal margin one-eighth of an inch.— lllawarra. 



18. Allorisma and***.— Transverse, very inequilateral, left valve 

 W«, front very broad and flattened, and having a narrow area ad- 

 joining the margin extending down from the beaks which is a little 

 concave; posterior prolonged and much compressed, narrowing and 

 somewhat recurved, gaping ; beaks very large and prominent, incurved, 

 contiguous ; lateral surface anterior to middle strongly flattened, or even 

 c °ncave ; surface unevenly plicate and having some faint radiations lat- 

 ely and posteriorly, plications large rounded and smooth, the alter- 

 <*te mostly becoming obsolete towards middle of lateral surface. 



L <*gth 4i inches height 6 3 L ; thickness tf* L ; the beaks ; are 

 »** more'prominent tha*n inTe A. curvatum, the posterior ex rem ty 

 m "ch narrower, the flank less inflated, and the front more abruptly trim- 

 ^^—Illatcarra. 



S ^o» s ER i ES , Vol. IV, No. 10,- July, 1847. 20 



