242 ANNALS NEW YORK ACADEMY OF SCIENCES 



Couvexity moderate, fairly prominent in the umbonal region. Sides de- 

 pressed, especially near the hinge, but without forming well-defined wings. 

 Bealv nearly central, somewhat posterior to the middle of the hinge. Axis 

 about parallel to the hinge line and the whole growth nearly symmetrioal. 



Surface marked by fine, fairly strong and sharp, subequal to somewhat 

 alternating radial costse, which extend obscurely onto the anterior wing, but 

 probably not onto the posterior. There are also moderately strong, irregular 

 and widely spaced concentric strife due to unequal growth and probably be- 

 tween these more or less distinct concentric striae of a finer character. The 

 concentric markings are more sharply expressed on the wings than on the 

 body of the shell. 



Astartella ? forresteri sp. nov. 



Shell small, subquadrate, nasute. Width about one and one third the 

 height. Cardinal and ventral margins slightly convex, almost parallel or 

 gently converging posteriorly. Posterior truncated with a slightly oblique 

 outline which tends to make a little more than a right angle with the car- 

 dinal outline and a little less than a right angle with the ventral 

 outline. Posterior inferior angle strongly rounded ; posterior superior angle 

 more or less distinct. Anterior extremitj'^ strongly projecting, in some speci- 

 mens about one third the entire width. The outline is concave above for 

 about one half the height, leaving the beaks small and incurved but rather 

 prominent. Convexity low ; valves occasionally somewhat compressed near 

 the hinge. Lunule and escutcheon large, shai-ply defined. 



Surface smooth, except for an occasional strong stria of growth near the 

 margin. 



The proportions vary considerably, some specimens being less trans- 

 verse than others. Another point of variation consists in the degree of 

 projection of the anterior extremity. The contraction of the upper and 

 lower margins varies likewise, those specimens in which it is strongest 

 having a less distinct cardinal angle. In extreme cases, the shape is 

 somewhat like that of an abbreviated Leda. This occurs where the 

 anterior portion is unusually long, the posterior unusually short, the 

 cardinal line oblique and the posterior superior angle not well defined. 

 So completely do these different modifications intergrade, however, that 

 it seems unwise to attempt to distinguish separate varieties. 



The dentition of this form is unknown, but the configuration is that 

 of our Carboniferous Astartellas. All the Astartellas, however, have 

 strong, concentric lamellge. Cypricardella (Microdon) has also much 

 the same shape, but these regularly have strong concentric striae. There 

 is no form in our American Carboniferous with which this species is 

 liable to be confused. 



I have the honor to name it for Mr. Eobert Forrester, of Salt Lake 

 City, who collected the specimens on which it is based. 



