46 STEIAN MOLLUSCAX FOSSILS. 



extremity subcaudate and obliquely truncate : ventral margin arcuate and 

 bebind slightly flexuous : umbones subterminal, angulated, sharp, contiguous, 

 strongly turned forward : lunule almost flat, slightly excavated at the upper 

 part, vertically roundly-elongate, bounded by a sharp margin : cardinal area 

 widely lanceolate, deep, limited on each side by a rather sharp ridge or keel; 

 outside of the ridges, on each side, a flattened area, separated from the con- 

 vex portion of the valve by an obtuse ridge running from the beak to the 

 postero-inferior extremity : surface marked with fine concentric stria) and 

 distant coarser lines of growth, all of which become heavier on the flat urn- 

 bonal declivity, the striae being replaced upon the beaks by about eight low 

 and regular varices : hinge apparently armed with three primary teeth, and 

 on the right valve with a distinct, remote posterior lateral tooth, straight 

 and elongate : muscular impressions clearly marked, but not deep : internal 

 margin thin and not crenulated. 

 Two specimens : — 



Larger: length, 51 mm.; height, 46 mm.; thickness, 3G mm. Coll. Bird. 



Smaller : " 4U mm. ; " 38^ mm. ; " 30 mm. Coll. Merrill. 



It seems probable that the species figured by Fraas under the name 

 Astarte Libanotica (Aus dem Orient, II. Theil, p. 45, PI. iii, figs. 1 a, b), and 

 said by him to be "one of the commonest shells in the horizon of the sand- 

 stone," is identical with this. But his figures represent the ante-umbonal 

 portion as considerably longer, the hinder extremity rounded rather than 

 truncate, and the posterior umbonal slope as wanting the flat surface which 

 is present in our specimens, and is bounded on one side by an obtuse ridge 

 running from each beak to the posterior-basal angle, and on the other by 

 the sharp ridge which limits the cardinal area. Our specimens are alike in 

 form and proportions, and while they and Fraas's figures may represent 

 divergent forms of one and the same species, yet since the uncertainty 

 in this respect is in no degree removed by any verbal description, and as 

 we cannot regard the shell as an Astarte, we feel warranted in describing 

 and naming it anew. 



Fraas's only semblance of description is contained in the following pas- 

 sage : " Characteristic of Astarte Libanotica are six to eight strong Astarte- 

 wrinkles next to the umbones, but which farther upon the shell Qatten out, 

 so that it appears nearly smooth. Without the aforesaid ribs, peculiar to 

 the genus Astarlc, from the aspect of the shell one would sooner think of 

 Venus and its related genera. Whether the margin of the shell is notched 

 or smooth, unfortunately I cannot affirm from any of the specimens." 



