240 The University Science Bulletin, 



moderately light; strengthening rod extends caudad to within a short distance 

 of the apex. No distinct teeth present, the ventral apical edge and the entii-e 

 dorsal edge except at the apex are slightly and irregularly roughened; area of 

 ducts conspicuous, granular in appearance, circular duct openings visible; open 

 along ventral apical edge and along dorsal edge for entire length, in the basal 

 region they open irregularly in the entire width of the valve. 



Sipanghergiella mexicana Baker. 



(PI. XXIX, fig. 6.) 



Length, 1.9 mm., greatest width, 0.27 mm. Cvu-ved base narrow and rodlike, 

 widens into broad, flat portion, about the same width for entire length, nar- 

 rowing caudad to apex; bears two prominences, one on dorsal edge somewhat 

 less than midway, and the other on the ventral edge about two-thirds the 

 length, more angular; not curved beyond the base, narrowed at tip evenly and 

 gradually by both curving edges, ends in sharp point, chitinization medium; 

 strengthening rod extends caudad almost to apex. Bears no teeth; area of 

 ducts granular in appearance, circular openings very small and inconspicuous; 

 open along ventral apical edge, at extreme apex, along dorsal edge, and in basal 

 portion of valve. 



Parabolocratus ^avidus Signoret. 



(PI. XXIX, fig. 7.) 



Length, 2.3 mm.; greatest width, 027 mm. Curved base narrow and rodlike, 

 widens gradually into broad, flat portion, about the same width for entire 

 length, narrowing only at apex; bears two broadly rounded prominences, one 

 on the dorsal edge about a third of the length, the other on the ventral edge 

 about two-thirds the length; only slightly curved beyond base, tip gradually 

 narrowed and ends in sharp point, chitinization medium; strengthening rod 

 extends caudad to within a short distance of the apex. Toothed only at ex- 

 treme tip; teeth are continuous around the tip, of these six are on the dorsal 

 edge and ten on the ventral edge; ducts inconspicuous, invisible except at ex- 

 treme apices, circular openings visible ; open along ventral apical edge and 

 along entire dorsal edge except in dorsal prominence. 



Aligia jucunda (Uhler). 



(PI. XXIX, fig. 11.) 



Length, L83 mm.; greatest width, 0.17 mm. Curved base narrow and rod- 

 like, slightly wider beyond base for a little more than half the length; apical 

 portion of valve widens abruptly, tapers caudad to apex; distinctly curved, tip 

 narrowed by curved dorsal edge, extreme apex bluntly rounded, almost square, 

 chitinization medium; strengthening rod extends caudad to within fourteen 

 dorsal teeth of apex. Toothed area on dorsal edge occuj^ies somewhat less than 

 the apical half; teeth eighty-eight in number, very small, wedge-shaped, fairly 

 regular in size, shape and spacing, bear small secondaiy teeth on outer edge, 

 one to four in number; tip devoid of teeth on ventral and caudal edges; area 

 of ducts conspicuous, granular in appearance, though a few elongate ducts are 

 visible apically; ducts straight, numerous; open along ventral apical edge, at 

 extreme apex, along dorsal edge of toothed area, and irregularly in the basal 

 region. The two valves of the pair are joined one to the other by an elongate 



