73 
2. LePT^NA ? NOBILIS, M‘Co7J. 
Lept(Bna [Stropliomena) nobilis, M‘Coy, 1852, Brit. Pal. Foss., p. 316, pi. 2a, fig. 2. 
j, nohilis, T. Davidson, 1865, Mon. Brit. Dev. Brach., p. 86, pi. 18, fig. 19-21. 
Shell subsemi-elliptic, usually a little wider than long, greatest width 
at the hinge line. Ventral valve rather strongly and regularly arched ; ears 
slightly depressed, projecting slightly beyond the sides, which form an acute 
angle, a little less than a right angle, with the hinge line, Tlie heak is small 
and hardly projects beyond the hinge line. The area does not appear to be 
well developed. The external surface is ornamented with a large number of 
radiating ribs, twenty to twenty-four of which have their point of origin in 
the beak, and extend more or less regularly to the margin without much 
modification in thickness ; between these ribs, and at different distances from 
the beak, others of the same form appear in sufficient number to present 
an almost equal space between them all — a distance of about a millimetre on 
the average ; the free [unribbed] space is wrinkled, but the ribs are not 
affected by it ; these wrinkles are more marked on the upper than on the 
lower portion of the valve ; they are covered by delicate strise parallel to the 
ribs numbering seven to nine to each division. The dorsal valve is concave, 
follows the contour of the opposite valve, and bears ornaments similar to 
those that cover the surface of the other. 
Dimensions. — Length, thirty-six millimetres ; width, forty-two milli- 
metres. 
Delations and Differences. — This species has some analogy to the pre- 
ceding, from which it differs in its greater size, the wrinkled surface, and the 
greater convexity of the ventral valve. 
Horizon and Localities. McCoy has found this beautiful sj)ecies 
in the Devonian limestones of Teignmonth, and Mr. Davidson has recorded 
it from the limestone of Woolborough, near NewTon Abbot. Of the two 
specimens that were sent to me by the Dev. W. [B] Clarke, one comes from 
Yarradong, and the other from the Yass District; they are enclosed in a com- 
pact blackish limestone that appears to me to belong to the Middle Devonian, 
one of the specimens preserving, as well as the Leptcena, a fragment of a 
crinoid stem, in all respects similar to that of Rliodocrinus crenatus, Goldfuss, 
which belongs to that formation. 
