254 The University Science Bulletin. 



also bears a single secondary tooth; margin of valve between primary teeth 

 notched with small secondary teeth; tip notched with small, irregular teeth 

 on both edges; area of ducts conspicuous, granular in doi-sal region, duct-like 

 in ventral region, circular duct openings visible; open at ventral apical edge 

 (seven), at extreme apex (one), along dorsal edge of toothed area, and in 

 basal region; the two valves of the pair are joined one to the other by a 

 distinct, elongate, heavily chitinized connection present on the dorsal edge of 

 the basal area and occupying about one-tliird the length. 



Phlepsius excultus (Uhler). 



(PI. XXIV, fig. i; pi. XXXII, fig. 9.) 



Length, 1.8 mm.; greatest width, 0.17 mm. About the same width for entire 

 length, tapers caudad to apex; bears a suggestion of a preapical prominence 

 in the ventral edge, extreme apex rounded, chitinization moderately heavy; 

 strengthening rod extends caudad as far as fourth dorsal tooth from apex. 

 Toothed area on dorsal edge occupies a little more than the apical third of 

 the length; teeth fifteen to seventeen in number, rather small, roimded, 

 fairly regular in size and shape but uneven in spacing; bear a few secondary 

 teeth on caudal edge, and a few primary teeth bear a single secondary tooth 

 on the cephalic edge, margin of valve between primary teeth bears small 

 secondary teeth; tip notched with small teeth on both dorsal and ventral edges, 

 practically continuous around the tip; eight large teeth on ventral edge; these 

 may be simple or may bear secondary teeth, irregular as- to arrangement; 

 area of ducts conspicuous, ducts elongate for the most part though a granular 

 area is present dorsally, duct openings visible; open along ventral apical edge 

 (six), at extreme apex (one), along dorsal edge of toothed area, and in the 

 basal region; the two valves of the pair are joined one to the other by a dis- 

 tinct, elongate heavily chitinized connection present on the dorsal edge of the 

 basal area, occupying more than a third of the total length, this connection 

 irregularly roughened along its dorsal edge. 



Phlepsius irroratus (Say). 



fPl. XXIV, fig. 5; pi. XXXII, fig. 8.) 



Length, 1.5 mm.; greatest wddth, 0.17 mm. About the same width for 

 entire length beyond curved basal attachment, narrows caudad to apex; pre- 

 apical prominence wanting; slightly curved, tip gradually narrowed, narrowly 

 rounded at extreme apex, chitinization moderately light; strengthening rod 

 extends caudad as far as second dorsal tooth from apex. Toothed area on 

 dorsal edge occupies a little less than the apical half; teeth nineteen to twenty 

 in number, of medium size, in the general shape of an obtuse triangle with 

 caudal edge longer than the cephalic and the apex rounded broadly, fairly 

 regular as to size shape and spacing, but not entirely so ; bear a few secondary 

 teeth on caudal edge and also a few bear a single secondaiy tooth on the 

 cephahc edge; tip is notched with small, indistinct teeth on both dorsal and 

 ventral edge, not continuous around the tip, about fifteen on ventral edge; 

 area of ducts conspicuous, granular in appearance, duct openings easily 

 visible; open along ventral apical edge (ten), at extreme apex (one), along 

 dorsal edge of toothed area, and in the basal region where elongate ducts are 



