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242 CRABS OF THE FAMILY PERICERIDZ—RATHBUN. 
This species and the preceding differ from all other species of Libinia 
in the prominent hepatic regions, and in the sharp postocular spine 
directed outward, characters which hardly seem to justify the formation 
of anew genus. Excepting L. rostrata Bell, they are the only species 
having long rostral horns in connection with closed orbital fissures, 
L. spinimana is peculiar in having spines on the hands. 
Libinia mexicana, sp. nov. 
Plate xxxI, fig. 3. 
Carapace pyriform, covered with a short pubescence and bearing 
twelve long spines besides the prieocular. Median spines four: two on 
the gastric region (the posterior the longer), one on the cardiac, and one 
on the intestinal. There is a small spine on each side of the anterior 
median gastric spine, a tubercle on the genital, and one on the cardiac 
behind the spine. There are two long spines on each branchial region, 
one on each side of the genital region, pointing outward and a little 
forward, the others further from the median line and nearly in line 
with the cardiae spine, but pointing backward and outward. Lateral 
spines two: one on the hepatic region, one on the anterior part of each 
branchial; further back on the margin there is an inconspicuous spiny 
tubercle. 
Rostrum rather long, nearly straight, the distal half bifurcated. Horns 
tapering; outer margins slightly divergent; interspace V-shaped. 
Orbits with an open fissure above and below; preeocular spine prom- 
inent; postocular well developed, obtuse. 
Basal antennal joint rather narrow, with a triangular acute spine at 
its distal extremity, pointing downward and forward. Second and third 
joints rather stout. Remaining portion wanting. There is a short spine 
and two or three tubercles on the pterygostomian region. 
Legs short, covered with a close pubescence; joints unarmed. Cheli- 
peds, in a young male, weak, almost as long as the first pair of ambu- 
latory legs. Palms compressed, not dilated. Fingers narrowly gaping, 
their distal half finely toothed. 
Length, without rostrum, 10™ ; breadth, 7.5™™; length of rostrum 
about 3.5™"; length of cheliped about 8.5™™, 
Collected in the Gulf of California, off Shoal Point, Mexico, near the 
mouth of the Colorado River, lat. 31° 33/ N., long. 114° 20’ 30” W., 104 
fath., fine gray sand, broken shells, station 5029, U.S. Fish Commission, 
1889 (16072). 
This species is nearest to LZ. smithii Miers, but differs in the narrower 
carapace, the less divergent rostral horns, the shorter ambulatory legs. 
The lateral branchial spine is also farther forward in mexicana, and the 
twelve long spines are nearly equal in length, while in smithii the car- 
diac, intestinal, and second lateral spines are longer than the others. 
The marginal spine of the basal antennal joint is wanting in mexicana, 
