25O NEW YORK STATE MUSEUM 



extremity), a Glenmont specimen (here partly reproduced in figures 151, 

 152) has seven to nine of them. The distinguishing characters of 

 D. Sagittarius, notably the short, broad form of the thecae, their large 

 overlap and large inclination differ little between the proximal part (D . 

 convexus) and the largest, distal fragments. We therefore believe that 

 we can hardly err in combining these specimens to obtain the following 

 description : 



Description. Rhabdosome consisting of two broad, long branches 

 (initial width .3 mm; greatest width 2.9 mm; length by inference 2.5+ m), 

 which in the proximal part rapidly increase in width (in 50 mm from .2 to 

 1 mm), but more distally are of nearly uniform width ; are declined in 

 direction, gently convex in the proximal portion, but early assuming a 

 rigidly straight direction ; forming an angle of inclination of 1 io° in the prox- 

 imal part and one of 8o° a. little more distally. The sicula is very small 

 (length = .8 mm), and inconspicuous but relatively broad. The first theca 

 appears to originate in the apical part ; this and the second theca (which, as 

 far as the evidence of the single specimen available goes, originates from 

 the first also near the apical extremity) diverge just above the aperture of 

 the sicula. The crossing canal is horizontal. The earlier thecae are narrow 

 and slender ; they number nine in 10 mm, overlap not more than one quarter 

 their length, and are inclined but 15-20"; but overlap and inclination 

 increase very rapidly and the thecae become rapidly wider. In the mature 

 parts there are but seven thecae in 10 mm; these overlap one half their 

 length, are almost half as wide as long and arc inclined at an angle of 25". 

 The outer margin is straight or gently convex ; the apertural margin like- 

 wise or slightly concave and rectangular on the axis of the theca. 



Position and localities. The type locality of the species is the Nor- 

 manskill (Kenwood) near Albany and its horizon the Normanskill shale. It 

 is there associated with I), subtenuis, etc. llall knew the species 

 also from the town of Stuyvesant and the neighborhood ol Hudson. Ai 

 the latter place it is common in the shales at Mt Moreno. It also occurs 

 at Stockport, near Poughkeepsie, in Canada, Arkansas and on the Dease 



