750 THE AMERICAN NATURALIST. [Vor. XXXV. 
ft. Body fusiform ; ridge high (one-fourth the diameter of 
the body). . . . . 165, M. carinata Ehr. (Fig. 115) 
fz. Body fusiform ; ridge low . . . 166, M. rattus Ehr. 
J3. Body cylindrical, elongated (length about four or five 
times the greatest diameter), slightly enlarged in front. 
Ridge low, hardly noticeable. Toe about the length of the 
brio vos ovs. 7, M. elongata Gosse (Fig. 116) 
22. Lorica with two parallel longitudinal ridges close together, 
with a groove between them. No teeth at the anterior 
margin of the lorica 
ft. The two ridges extending three-fourths the length of the 
body, which is fusiform in shape ; toe very long, straight 
168, M. bicristata Gosse (Fig. 117) 
f2. The two parallel ridges close together and extending 
only one-half the length of the lorica ; body shorter, ovoid, 
or oblong in side view . 169, M. mucosa Stokes (Fig. 118) 
£3. Lorica without a ridge, cylindrical, ovate, or conical. (See 
also No. 167, M. elongata) 
ft. One or more teeth or spines present at the anterior 
margin of the lorica 
£I. Two unequal teeth or spines at the anterior margin 
of the lorica ; body long-fusiform 
170, M. bicornis Ehr. (Fig. 119) 
£2. Two sharp, slender, equal spines close together at the 
anterior margin of the lorica; body a cone, largest in 
front and tapering to a toe about one-fourth the length 
ofthe body . 171, M. birostris Minkiewicz (Fig. 120) 
£j. A single large median tooth projecting over the head 
from the anterior dorsal margin of the lorica. Body 
cylindrical, somewhat curved ; toe little more than half 
as long as the body 
172, M. capucina Wierz. & Zach. (Fig. 121) 
£4. A single short broad median tooth from the anterior 
dorsal edge of the lorica. Body ovate-fusiform, nearly 
symmetrical, constricted anteriorly to form a cylindri 
neck. Toe not so long as the body ; 
173, M. multicrinis Kellicott (Fig. 122) 
f2. Anterior dorsal margin of lorica smooth, without teeth 
£1. Body very broad, ovate, compressed dorso-ventrally, 
unsymmetrical ; toe four-fifths the length of the body 
174, M. lata Jennings (Fig. 123) 
g2. Body short and thick, arched dorsally, nearly flat 
ventrally ; lateral antennæ, at the posterior lateral pus 
of the lorica, protected by two prominent projecting 
spines ; toe longer than the body 
175, M. bicuspes Pell. (Fig. 124) 
