132 RECORDS OP THE AUSTRALIAN MUSEUM. 



Myodoka pavimenta, sp. nov. 

 (Plate xl., fig. 3). 



Shell transversely elongate, posteriorly truncate, thin, cora- 

 preased. Colour uniform pearl gray, towards tlie umWo of the right 

 valve are a few opaque radial streaks on a translucent ground. 

 Right valve shallow, left slightly concave, especially round the 

 margins. In both valves a broad posterior area is sharply 

 defined. Ventral margin rounded, forming an obtuse angle at 

 the intersection of the po.sterior ray, truncated end straight, 

 broad, slightly oblique to the axis of the shell, forming a right 

 angle with the posterior dorsal concave margin. Umbo acute, 

 incurved. Anterior dorsal margin nearly straight, meeting the 

 ventral margin in a blunt angle. Sculpture : a decided keel runs 

 from the umbo to the postero-ventral angle. From this branch 

 about a dozen widely spaced concentric ridges, similar to the 

 radial, these gradually fade on the anterior side. On the left 

 valve a furrow corresponds to the radial ridge. Length, 14 ; 

 height, 8 ; depth of conjoined valves, 2 mm. 



Hab. — I dredged three specimens alive in five fathoms, in 

 Van Dieraen Inlet, Gulf of Car[)entaria. About five hundred 

 and sixty miles to the north-north-west, the " Challenger " dredged 

 an un-named species, closely related and perhajis identical 

 with this^. In 15 fathoms, ofif the Palm Islands, Queensland, I 

 dredged several dead and mostly small specimens. 



i Myodora tessera, s/>. nov. 



(Plate xl., fig. 4). 



Shell large, thin, compressed, equiUteral, sub-rhomboidal. 

 Posterior dorsal margin concave, anterior dorsal margin straight 

 in the young, convex in the adult. Colour uniform cream butf; 

 both valves brilliantly nacreous within. Left perfectly flat, 

 right very shallow. Sculpture : on both valves shallow, l)road, 

 irregularly spaced, concentric corrugations, abruptly limited 

 by a posterior ray which is bordered in the flat valve by a 



" Smith— Chall. Rep., Zool., xiii., 1885, p. 66. 



