NATURAL SCIENCES OF PHILADELPHIA. 227 



between the eighth and ninth on the upper margin ; those witli 

 but nine teeth on the superior margin have the first below under 

 the sjDace between the fourth and fifth ; the last midway under the 

 space between the seventh and eighth of the superior margin. 

 Inner free flagella of a deep red color. Anterior pair of legs slen- 

 der and delicate ; carpus more than twice the length of the baud ; 

 hand slightl}^ pubescent ; second pair of legs slender, smooth on 

 the upper surface ; under surface beset with very minute spiniform 

 granules, seen onl}^ through the lens ; carpus longer than the hand, 

 twice the length of the palmar portion of the hand ; fingers cj'lin- 

 drical, straight, less than half the length of the hand ; posterior 

 legs smooth. Length 2.81 inches. 



This species is very closely allied to P. mexicanus (Saussure), 

 and may prove to be nothing more than a vai-iety of that species. 

 The measurements of the second pair of legs of P. sexdentatus 

 agree with De Saussure's description, but differ widel}' from the 

 measui'ements of his figure. P. mexicanus has but four or five 

 teeth on the inferior margin of the rostrum. The terminal segment 

 of the abdomen in P. sexdentatus is armed with three small teeth, 

 and two longer movable spines situated one on either side of the 

 middle tooth ; the hand is verjr largely beset with hairs. 



Habitat. — Same as the preceding. 



PALiEMON FLUVIALIS, nov. sp. 

 Plate II. Fig. 5-5a. 



Rostrum short, lanceolate, somewhat arched above ; not as long 

 as the lamelliform appendages of the external antennte, reaching 

 to the end of the second joint of the antennae ; superior margin 

 armed with seven teeth, the inferior margin with two, situated 

 near the point of the rostrum. One specimen of this species had 

 but four teeth above and one below. Two flagella of the internal 

 antennae united for a very short distance ; spines on the lateral 

 portion of the carapax very small ; first pair of legs slender ; hand 

 more than half the length of the carpus ; hand of the second pair 

 stout ; carpus shorter than the palmar portion of the hand, gradu- 

 all3'' enlarged toward the hand ; fingers cylindrical and straight, 

 shorter than half of the hand, the same length as the carpus, beset 

 with a few stiff" hairs; legs smooth. Length 1.3 inches. 



This is a fresh-water Pal^mon, taken from a tributary of the 

 Coatzacoalcos River among the Cordilleras. 



18tl.] 



