050 NEW SPECIES OF EKESH-WATER CRABS RATHHUN. 



into two lobes. Seen from in front, tlie margin is nearly horizontal; 

 seen from below, the two lobes are slightly arched forward. There 

 is no outer orbital fissure. The frontal and upper orbital margins are 

 indistinctly ridged, and are granulate in small specimens; in large ones 

 the ridge is uneven, the normal granulation being feebly indicated. 

 Lower orbital margin granulate. Anterolateral margins finely den- 

 ticnlate, the denticles obsolete in adult males, where the margin is 

 simply uneven. Ischium of maxillipeds elongate, merus subtriangular, 

 endognath but slightly overlapping the jugal area; exognath shorter 

 than the ischium (PI. lxxiv, Fig. 3). The inferior surface of the body 

 is punctate, the puncta^ being larger next the orbit. The cervical 

 suture is present on the lower surface. The abdomen of the male 

 (Fig. .1) is widest at the distal end of the third and the proximal end 

 of the fourth segment; lateral margins of third and fourth segments 

 convex, of fifth concave. Fxtremity of appendage of first segment 

 with lateral expansions above, the outer one larger and with a single 

 sharp tooth pointing outward and downward, the inner one with a 

 spatulate tooth pointing forward and inward (Fig. 2). The abdo- 

 men of the female conceals the sternum. Chelipeds very unequal. 

 Merus with short, stout spines on the inner margin; upper margin 

 with dentiform tuber(;les on the proximal two-thirds; lower outer mar- 

 gin rounded, with a few granules; a line of granules on the inner sur- 

 face near the carpus. Carpus punctate, with a short, broad longitu- 

 dinal groove above and a stout inner spine. Larger hand in male 

 much inflated, punctate, smooth; fingers widely gaping, with strong 

 teeth. Smaller hand with margins subparallel, fingers almost meeting 

 when closed. In the females the chelipeds are more nearly equal, and 

 in character resemble the smaller cheliped of the male. Ambulatory 

 legs little compressed; merus slender, with upper and lower margins 

 subparallel, upper margin blunt, with depressed spinules, which be- 

 come obsolete in adults; carpus feebly spinulous above; propodus, 

 above and below. 



(^olor, a rich reddish brown. 



Length of $ 27"""; width, 43.5; length of large chdiped, 86. Length 

 of ? 29;^ width, 4(>; length of large cheliped, GG. 



Many specinu>ns were collected by Mr. P. Ti. .l<my in 1H!)2 at the 

 following localities in Mexico: 



Lake Chapala, about 5,000 feet elevation, among stones and shingle 

 on lake shoie; February 19, 7 5 , 80 ? , mostly with eggs (17718); 

 Febiuary 20, 7 5,2 ? , 4 young, all small (17719). 



Jnanacatlan, Falls of Kio San Juan, between Lake Chapala and 

 Guadalajara, April 26; 6 5,11 ?, mostly small (17720). 



Prof. A. Duges has presented specimens from Valle de Santiago, 

 State of (luanajuato; 1 5,1 ? (17721); also an additional female 

 (4122) from the same State, probably from the same locality. 



This species bears a strong resemblance to P. americana Saussure 

 from Hayti, but that species is without a cervical suture. 



