228 ANNALS NEW YORK ACADEMY OF SCIENCES 



long as the greatest width, much longer behind than in front. Outline broadly 

 and regularly rounded below and in front, curving strongly inward toward the 

 hinge, where it is slightly straightened. On the posterior side, it is convex 

 below and concave above, sloping strongly outward in a gentle curve below 

 the broad posterior wing. Convexity moderately high. Anterior wing small 

 and undefined. Posterior wing large, triangular, usually though not always 

 abruptly depressed and distinctly defined. 



The sculpture consists of fine regular concentric undulations or strife and 

 fine radiating lirse. The undulations are shallow and rounded, and they are 

 broad in comparison with the angular ridges which separate them and which 

 are lamellose at least toward the sides. The radial sculpture is on a finer 

 scale than the concentric, subordinate to and more or less interrupted by it. 

 The radii are very fine and slender with relatively broad interspaces.' They 

 seem to die out toward the posterior side of the left valve and to be replaced 

 by a few of larger size on the posterior wing of the right valve. 



Aviculipecten squamula sp. nov. 



Shell small, the largest specimen referred here having a length of 7 mm. : 

 length and width about equal ; slightly oblique, somewhat inclined backward. 

 Hinge line but little shorter than the greatest width. Outline gently con- 

 tracted below the hinge, then widening again. Lower extremity broadly 

 rounded. Convexity low. Wings broad and undefined, the posterior one hav- 

 ing perhaps for its boundaiy a low, narrow fold extending obliquely from the 

 umbo to the posterior margin not far below the hinge line. 



The sculpture consists of fine, regular, concentric striae crossed radially by 

 fine irregular costse so obscure that they are made out with more or less difli- 

 culty. They are interrupted and obscured to some extent by the concentric 

 markings. 



Aviculipecten jennyi sp. nov. 



This form resembles A. squamula, having a subquadrate shape, a hinge 

 nearly as long as the width below, and subparallel sides with scarcely any 

 deflection defining the wings. The convexit:^^ is low. The umbo small and in- 

 conspicuous and the axis nearly perpendicular to the hinge line. In one speci- 

 men, the posterior wing has a fold as in" A. squamula. 



The sculpture consists of somewhat irregularly distributed costse with rela- 

 tively broad, flat interspaces. The costse, though low and rounded, are well 

 defined, but they do not extend onto the wings. Thei'e are also very fine, 

 equal, closely arranged, concentric lirje and numerous stronger incremental 

 stria?, especially conspicuous over areas near the hinge where the costse are 

 not developed. 



Aviculipecten multilineatus sp. nov. 



Shell small and subquadrate, about as in A. squamula, which is closely 

 related. Convexity moderate ; hinge long, but little shorter than the greatest 

 width, which is about equal to the greatest length. Umbo moderately ele- 

 vated. Axis but slightly oblique, inclined backward. The wings are large, 

 subquadrate and poorly defined either upon the surface or by any deflection 



