214 A^'NAL8 NEW YORK ACADEMY OF SCIENCES 



When determinable, from 6 to 8 seems to be tbe number, which varies accord- 

 ing to the width. In parts of some specimens, the zooeeial openings seem ta 

 occur in rows which are neither longitudinal nor transverse but slightly in- 

 clined from a strictly longitudinal direction. The apertures are circular or 

 slightly elongated, and, when not worn down, their margins are elevated in 

 such manner as to give the surface a strongly pustulose appearance. Longi- 

 tudinally about 4 apertures and 4 interspaces, or 5 apertures and 4 interspaces 

 occur in 2 mm. They are separated on an average by intervals which are 

 about equal to their own diameters (about .17 mm.), but vary from consider- 

 ably less to double the diameter. The intervals between the apertures are 

 smooth. Of longitudinal furrows or ridges there is no trace. In fact, the 

 irregular distribution of the apertures would hardly be correlated with such 

 superficial markings. 



Orthotetes subglobosus sp. nov. 



Shells attaining a rather large size, maximum width about 50 mm. Shape 

 semicircular, transverse. Cardinal angles often rounded so that the greatest 

 width is a little in front of the hinge. 



Ventral valve generally flat or slightly concave, moderately elevated pos- 

 teriorly, rarely distorted. Cardinal area nearly perpendicular to tbe plane of 

 the margins. Pseudodeltidium narrow, higher than broad with a sulcus down 

 the middle. Upon the inside, a long median septum unites with the two dental 

 plates, thus forming with the pseudodeltidium a small chamber. 



Dorsal valve convex. Often highly inflated, especially in the umbonal 

 region. 



Surface marked by thin, sharp radii separated by relatively broad, flat in- 

 terspaces, crossed by rather strong, coarse, crenulating line. The radii are 

 often strikingly and regularly unequal. In number and appearance, they vary 

 greatly owing to the number of intermediate ones that happen to be present. 

 In some specimens, only about 7 large subequal lirse can be counted in 5 mm., 

 having broad interspaces between : in others. 7 with alternating small ones 

 occur: and in still others, 1?> or 14 rather fine subequal ones: but in still others, 

 the latter nimiber can be observed alternating with very fine initial liroe. As 

 new lira? are not interpolated with absolvite regularity', the count varies much 

 within the broad limits indicated, depending not only upon what lira* are 

 actually present, but also upon how many are regarded as primary and sec- 

 ondary, or even are sufficiently well dev-eloped to be counted at all. 



Orthotetes subglobosa var. protensa var. nov. 



This variety is based upon a single specimen distinguished principally by 

 having a more elevated and distorted ventral valve than the normal. The 

 height of the pseudodeltidium must have been about 11 mm. and a width below 

 of 7 mm. The area is rather strongly inclined to the plane passing through 

 the margins of the shell. 



This specimen was found associated with a ventral valve having the 

 low area and regular growth of the typical form, of which it will prob- 



