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301 
lateral tooth of moderate development, about 
equal in length to rounded portion; squamous 
portion reaching to end of antennular peduncle. 
Carpocerite slightly longer than both anten- 
nular peduncle and scaphocerite; flagellum 
somewhat longer than body. 
Mandibles of normal form but bearing a large 
oval black spot on the body of the mandible; 
black spot with sharp margins and persistent 
even after preservation in alcohol. Maxillule 
with outer lobe without setae or spines, but 
with two heavy, thickened lobes, somewhat sim- 
ilar in form to a bottle opener. Other mouth 
parts showing only minor differences from those 
normal to the family. 
Chelipeds symmetrical, enlarged. Ischium 3 
times as long as broad, bearing on superior 
margin a row of short spines, on inferior mar- 
gin a row of setae. Merus unarmed, 5 times as 
long as broad, slightly over twice length of 
ischium. Carpus subconical, proximally small 
in diameter, distally 3 times the proximal diam- 
eter; distal margins somewhat collarlike around 
base of propodus; articles without spines. Palm 
of chela somewhat inflated, subcircular in cross 
section, 1.6 times as wide at maximum diam- 
eter as long. Fingers long, slender, curved, 1.5 
times length of palm; proximally both fingers 
armed with low, widely spaced teeth. 
Second legs long and slender, ischium and 
merus equal in length and both about 10 times 
as long as broad. Sum of lengths of first three 
carpal articles equal in length to merus; ratio 
of the carpal articles is 10:3.5:8:3.5:5. Fingers 
of chela subequal in length to last carpal article, 
slightly longer than palm. 
Third legs slender. Ischium unarmed, except 
for scattered setae, almost 4 times as long as 
broad. Carpus unarmed, 0.8 as long as merus, 
about 0.6 as broad. Propodus also slender, 
slightly curved, tapering very slightly distally, 
1.1 times as long as carpus, and bearing 10 
slender, fine spines along inferior margin. 
Dactylus simple, slender, acute, 0.2 as long as 
propodus. 
Fourth and fifth legs similar to, but pro- 
gressively longer, than third. "Brush” on propo- 
dus of fifth legs well developed. 
Telson twice as broad at base as at tip, and 
3 times as long as broad at tip; lateral and 
terminal margins almost straight; dorsal surface 
slightly convex. Spines heavy with medial pair 
of terminal spines about as long as tip is broad; 
lateral pair slightly shorter; middle portion of 
tip with small tuft of plumose setae. Uropods 
normal in form, lateral spine of outer branch 
strong. 
Color in life from a brilliant to a pale salmon 
red, with the black mandibular spot conspicuous. 
DISCUSSION: These specimens show a varia- 
tion in the form of the chelipeds reminiscent of 
the species of Athanas. Mature males and fe- 
males have chelae as described above; slightly 
smaller specimens of both sexes have a large 
and a small chela (Fig. If, s); small specimens 
have both chelae similar to the smaller one of 
the asymmetrical pair. No other marked varia- 
tion was noted with sex or maturity. 
The differences between this species and M. 
minutus are few but conspicuous (contrast Fig. 
1 and Fig. 2). The stylocerite of M. lohena 
reaches to the end of the first antennular article, 
that of M. minutus to the middle of the second; 
the scaphocerite reaches to the end of the an- 
tennular peduncle on this species, to the middle 
of the third article on M. minutus. More im- 
portant are the differences in the chelae, with 
none of the numerous specimens of M. minutus 
showing the enlarged chelae; and with the 
fingers in all definitely shorter than the palm, 
while in M . lohena both the large and small 
type of chela have fingers longer than the palm; 
also, in M. minutus the fingers are quite straight 
and heavy, while in M. lohena the fingers are 
slender and show at least some curvature. An- 
other possible difference is the degree of cover- 
age of the eyes, with the eyes completely con- 
cealed in all specimens of M. lohena, and with 
them usually protruding in some degree from 
under the carapace in M. minutus; however, as 
the eyes may be rolled forward and backward, 
this characteristic should not be relied upon. 
There are no other conspicuous differences in 
the morphology of the two species. The color in 
life of the two species, including the black 
mandibular spot, is the same. 
They are also similar in their environments. 
The habitat of M. lohena is described above; 
while surface layers of the water in the undis- 
turbed pond were almost fresh, the under layers 
