FA rXA OF MAMMOTH CJA VE—HA Y. 229 



pair is the larger. They are probably slig-htly longer but more slen- 

 der. The proximal half of the limb presents no unusual charaeters, 

 ])ut the distal half has the characters peculiar to the Atyida\ The 

 proximal end of the carpus is slender and subcylindrical, but toward 

 the distal end on the superior surface there appears a thin plate or 

 ridge which gradually increases in height to a point just short of the 

 distill end of the segment. Here it is abruptly excavated so as to pre- 

 sent a broad sinus for the reception of the knob-like extremity of the 

 hand. Below this sinus the carpus extends forward a short distance 

 so as to articulate with the ventral surface of the hand and not its 

 proximal end. The hand is subcylindrical, the postarticular portion 

 is rounded, and, as stated above, is intended to fit closely into the sinus 

 in the carpal expansion. The fingers are so curved as to meet only at 

 their tips. They are apparently quite cylindrij,al and unarmed except 

 at their tips, where they bear each a dense pencil of rather long, 

 stiff, pluiuose or pectinate hairs. The hands and carpal segments are 

 usually directed downward and l)ackward so as to In-ing the ventral 

 finger to the lower side, and the degree of motion between the hand 

 and the carpus seems to be very great. 



The dactyls of the last three pairs of pereiopods are minutely ser- 

 rate, as are the distal extremities of the antepenultimate segment. 



The gills seem to be only four in number, on each side attached to 

 the first four pereiopods, but there may be a rudiment on the fifth. 



Twelve specimens w-ere secured, varying in length from 14 to 28 

 mm. from the tips of the rostrum to the end of the telson. In life 

 they were colorless, but in alcohol they are milk white. 



When I first described this genus and species 1 was of the opinion 

 that its affinities were with the Pala?monid{e and the genus PaJsenionetes, 

 and the name Palse/monias was given to call attention to the fact. I 

 had noticed the striking resemblance of the hand and carpal segment 

 of the first two pairs of pereiopods to the similar parts of certain of 

 the Atyidw, but did not consider this a character of sufficient weight to 

 overbalance the striking resemblance to certain of the Pala3nionid{e in 

 every other character. I have recently received a letter from Dr. 

 A. E. Ortman, of Princeton Univei-sity, calling my attention to other 

 characters, and, furthermore, I have been able to secure the descrip- 

 tion of Troglocarlsschinklt! Dormitzer,^ and have thereby been forced 

 to reverse my opinion. 



Paimtionim should certainly be placed in the family Atyidje, and is 

 a very close relative of the genus Xlphocarh, from which it seems 

 to differ by only one character, namely, the pronounced excavation 

 of the carpal segments. I would not be willing to accept as a good 

 generic character that of rudimentary eyes, as has l)een don(> in this 

 family for the genus Troglocaris. 



1 Lotos, 3d year, 1853, p. 85, pi. iii, fig. 1-5. 



