LAMELUBRANCIUATA. 37 



AvHTl.ni'Ki'TKN 0BNAT08. 

 PLATE II. FIGS 7. B; \m> PLATE III, Hi. n 



Aviculqpecten ornatus, Hall. Pal. N. v.. vol. \. pi. l. Plates and Explanations: PI. 2, figs. 7. 8; pi. :t, 



fig, M. Jan., L88S. 



Shell small, longitudinally oblique-ovate, sub-rhomboidal ; length ami width in 

 the proportion of three to four; margins regularly rounded. 



Valves depressed-convex-; left valve somewhat more convex than the 

 right, and a little larger. 



Hinge-line straight, slightly less than the length of the shell, central with 

 regard to the body of the shell. 



Beak obtuse-angular, directed forward, situated a little anterior to the 

 middle. 



Ears sub-equal. Posterior one the larger, triangular, Mat or concave, 

 defined by the abrupt post cardinal slope of the umbo; extremity acute; 

 margin concave. Anterior ear defined by a deep sulcus ; byssal sinus deep, 

 more strongly marked in the right valve. 



Test of the left valve ornamented l>\ about 25 Btrong, sharp, elevated rays, 

 and wide interspace's which are marked with a smaller ray : crossed by 

 undulating, concentric striae which are curved backwards between the 

 stronger rays, producing arched fimbriae. The right valve shows the 

 radiating stria' originating near the umbo, which is smooth, and increasing 

 l>v a double bifurcation, giving them a fasciculate appearance; they are 

 crossed hv undulating, concentric BtrisB. The ears are marked by strong, 

 radiating lines and line, concentric striae. 



Internal characters not observed. 



The length of the largest specimen is IS mm., height nearly 1 •"> mm., 

 and hinge-line about IT mm. 



This species, in form and general appearance, is \cr\ similar to A. Indus; it 

 differs conspicuously in the ornamentation, with proportionally shorter posterior 



