230 The University Science Bulletin. 



prominence and extreme apex; ducts conspicuous, decidedly cui-ved, numerous, 

 most numerous apically; open apically and along dorsal edge in and near 

 teeth, one to three to each tooth. 



Oncometopia lateralis (Fabricius). 



(PI. XXII, fig. 4; pi. XXVI, fig. 5.) 



Length 1.66 mm.; greatest width, 0.2 mm. Narrow and rodlike at the base, 

 widens beyond base into broad, flat apical shaft, which tapers very slightly 

 toward apex; preapical prominence present, rather indistinct, broadly rounded; 

 only very slightly cui-ved beyond the base, tip broadly rounded, chitinization 

 medium, strengthening rod extends caudad as far as last dorsal tooth. Toothed 

 area on dorsal edge occupies the entire length of the apical shaft; teeth eigh- 

 teen to twenty in number, large, subquadrate in shape with the cephalic side 

 longer than the caudal and bearing a smoothly rounded prominence, regular, 

 evenly spaced, more heavily chitinized than the rest of the valve and have 

 the appearance of being set into the rest of the valve; bear secondary teeth, 

 seven to fifteen on the broad outer edge and four to eight on the cephalic 

 side, those on the outer edge larger than those on the cephalic side; the tip 

 is notched with small teeth on both dorsal and ventral edges, not continuous 

 around the tip, twenty-one teeth between preapical prominence and extreme 

 apex; ducts conspicuous, elongate, distinctly curved, numerous, most numerous 

 apically ; open apically, along the dorsal edge in and near teeth, two to four to 

 each tooth; first three teeth not served with ducts. 



Homalodisca triquetra (Fabricus). 



(PI. XXII, fig. 5; pi. XXVI, fig. 6.) 



Length, 2.6 mm.; greatest width, 0.33 mm. Narrow and rodlike at base, 

 widens beyond base into broad, flat portion, which is about the same width 

 for entire length, narrowing only at apex; preapical prominence present, 

 distinct, broadly rounded; uncurved beyond base, extreme apex broadly 

 rounded, chitinization medium; strengthening rod extends caudad as far as 

 third dorsal tooth from the apex. Toothed area on dorsal edge occupies the 

 entire length of the apical shaft; teeth forty-four to forty-five in number, 

 medium in size, of a general triangular shape with the caudal side longer than 

 the cephalic, regular in size and shape, evenly spaced, more heavily chitinized 

 than the rest of the valve ; bear secondary teeth, three to seven on the cephalic 

 edge and five to nine on the caudal edge; those on the caudal edge are larger 

 than those on the cephaUc edge; tip notched with small teeth on both dorsal 

 and ventral edges, not continuous around the tip, ducts conspicuous, numerous, 

 slightly curved, most numerous apically; open apically along the dorsal edge 

 in and near teeth, two to five to each tooth; the first six teeth not served by 

 ducts. 



Aulacizes irrorata (Fabricius), 



(PI. XXII, fig. 6; pi. XXVI, fig. 7.) 



Length, 2.9 mm.; greatest width, 0.44 mm. Narrow and rodlike at the base, 

 widens beyond base into broad, flat, apical shaft; reaches point of greatest 

 width about two-fifths of length and from that point tapers gradually to the 

 tip; preapical prominence present, conspicuous, obtuse-angled; not curved 



