154 Fossils from Australia. 



Cleobis, (nov. gen.) — Shell inequivalve, inequilateral, thick, tran^ 

 verse subovate, closed (or nearly so.) Beaks large, salient and incurved. 

 Posterior margin broadly rounded and a little dilated. Ligament in- 

 ternal. Hinge line flexed to one side at middle and passing beneath 

 the lower of the beaks. Valves thin. Surface marked unevenly with 

 regular concentric striee of growth and without radiations. — This genus 

 appears to be near the Ceromya of Agassiz ; but of this we cannot be 

 certain, as the palleal and muscular impressions are not visible. There 

 is much external resemblance to the Avicula cuneiformis of Verneuil, 

 (Russia, pi. xli.) The beaks are prominent and incurved, but are not 

 flexed at all forward ; they project over or overhang the cardinal line, 

 the summit being separated from it by an intervening space. The 

 valves are quite thin, the thickness being less than a line in a large 

 species measuring seven inches in length. 



19. Cleobis grandis. — Thick, very convex, right valve largest ; front 

 very abrupt; anterior part about one-third the whole length; inferior 

 margin regularly arcuate ; surface concentrically striate and a little un- 

 dulate. — Length of large specimens seven inches, height j^L ; thick- 

 ness y 6 ^ L ; apical angle 105° — lllawarra. 



20. Cleobis gracilis. — Resembling C. grandis, but more projecting 

 anteriorly ; anterior portion, about two-fifths the whole length. — Length 

 2*9 inches ; height $& L ; thickness -^ L ; apical angle 125" 

 lllawarra. 



21. Cleobis! recta. — Subelliptical, somewhat compressed; lateral 

 surface flattened ; marked with concentric lines of growth ; inferior 



M 



margin straight at middle, parallel with dorsal; postero-dorsal margin 

 much dilated. — Length 3^- inches ; height probably y 6 ^ L ; thickness 

 tVtt L. The straight lines of growth over the medio-lateral surface, 

 and straight medio-inferior margin give a peculiar character to this 

 species. — lllawarra* 



22. Astarte gemma. — Transverse, very nearly equilateral, surface 

 evenly convex, delicately marked with deep concentric stride, margin 

 of the valves crenulate within ; large anterior muscular impression a 

 little excavate, transverse and suboval ; smaller anterior excavate, ob- 

 long; posterior rather faint ; palleal impression faint but distinctly with- 

 out a sinus, and quite reaching the anterior muscular impression; sur- 

 face of cast smooth.— Length'f inch ; height -^d L; thickness T Vff L 

 anterior part T 7 F of the whole length ; apical angle 140°. The impres- 

 sion of two divergent teeth is finely preserved. — lllawarra. 



The following species have the entire palleal impression, two ante- 

 rior and one posterior muscular impressions, and the external ligament 

 of Astarte. Yet the form is more transverse and inequilateral than is 



tic of that genus, and the ligament is longer, occupying the 

 whole cardinal area. The beak of an interior cast has the summit ob- 

 liquely truncate, and the lateral surface just posterior to middle is more 

 or less flattened. The large muscular impressions are broad sub- 

 elliptical or suborbicular, with the upper side often straight. The 

 smaller anterior is situated under the beaks as in Astarte. The ex- 



characters 



terior surface is concentrically striate. The valves at middle are qurtjj 

 thin, hardly -fa of an inch in the first of the following species, and 

 they thicken below towards the margin, where the same species $ 



