1885.] PROCEEDINGS OP UNITED STATES NATIONAL MUSEUM. 175 



scribed by Stimpson as the gastric tooth, and not referred to in con- 

 nection with the rostral teeth, which explains the apparent discrepancy 

 pointed out by Miers (Proc. Zool. Soc. London, 1878, p. 304) between 

 Stimjison's description and the specimen in the British Museum. The 

 surface of the posterior part of the branchial regions of the carapax 

 and of the whole of the pleon, except a very narrow and inconspicuous 

 line of pubescence either side of the dorsal carina of the fifth and Sixth 

 somites, is entirely naked and glabrous. The dorsal carina of tbe fourth 

 and fifth somites of the pleon is divided by a narrow incision like that in 

 P. Goodei, but not quite as deep. The telson is shorter than the sixth 

 somite and rather suddenly tapered to a short acuminata tip armed 

 either side with a short and very small spine. 



Variety similis. 



There are four specimens, one male and three females, taken by the 

 Albatross, station 2121, February, 1884, Gulf of Paria, north latitude 

 10° 37' 40", west longitude Clo 42' 40", 31 fathoms, which appear to 

 represent a distinct species very closely allied to P. constrictus, but as 

 a large series of specimens from the West Indies would very likely 

 show them to be only a variety, I describe them here as such. 



These specimens are a little larger than the largest observed speci- 

 mens of constrictus, and the rostrum somewhat longer, more slender, 

 and armed with eight or nine teeth in addition to the one on the gastric 

 region. The whole surface of the carapax and of the fourth, fifth, and 

 sixth somites of the pleon is thickly covered with very short, and stiff 

 seise, like those on the anterior portion of the carapax of P. constricfus, 

 and the surface itself, after the removal of the setie, is thickly punctate. 

 The telson is considerably longer than the sixth somite of the pleon, 

 and tapers very gradually to a very long and slender tip armed either 

 side its base with a long and very slender spine. 



Measurements of two of these specimens and of two of the largest 

 observed specimens of the typical constricUis are given in tbe accom- 

 panying table : 



Measurements in millimeters. 



P. constrictus. 



Var. similis. 



Catalogue number. 

 Station 



Sex 



Length from tip of rostrum to tip of telson 



Length of carapax including rostrum 



Length of rostrum 



Height of carapax 



Breadth of carapax 



Length of eye-stalk and eye , 



Greatest diameter of eye 



Length of antennalscale , 



Breadth of antennal scale 



Length of first perteopod 



Length of merus ; 



Length of carpus 



Length of chela 



d 



51 



18.5 

 7.2 

 7.0 

 6.0 

 4.3 

 3.0 

 8.8 

 3.2 

 9.5 

 2.4 

 2.3 

 2.1 



8870 

 2{i85 



26.5 



10.0 

 9.6 

 9.0 

 6.0 

 4.1 



11.3 

 4.0 



l.\ 

 3.6 

 3.2 

 3.3 



7265 

 2121 



d 



62 



22.7 

 9.0 

 8.0 

 7.5 

 5.2 

 4.5 



11.0 

 3.6 



12.5 



3.0 

 3.0 



7265 

 2121 



31.0 

 13.3 

 11.7 

 10.1 

 7.0 

 5.2 

 1».4 

 4.8 

 18.0 



