HETEROCARPUS HOSTILIS. 151 
a single specimen procured by the “Challenger” in 700 fathoms among 
the Philippine Islands.* The habitats of the two species are separated by 
the whole breadth of the Pacific Ocean. 
Compared with H. gibbosus, its western representative, H. vicarius, differs 
as follows: the carapace is very much longer both in proportion to its own 
height and to the length of the rostrum, and its dorsal margin is not so con- 
vex; the teeth of the upper edge of the rostrum are more numerous and 
closely set ; the lateral carinz of the carapace are more prominent; the third 
abdominal segment forms a sharper angle or knee; and the antennular 
flagella are longer and subequal in length. 
In 7. vicarius the third maxilliped is not furnished with an exopod. In 
place of it there is merely a small papilla on the outer side of the basipodite. 
This is also the case in the type of 1. oryx and, according to Bate, in H. dor- 
salis. In H. hostilis and H. affinis the exopod is present, though rudimentary, 
being not more than one fifth as long as the ischium. In other species, e. g. 
ensifer, carinatus (= ensifer ?), alexandrt, and levis, the exopod forms a promi- 
nent appendix to the third maxilliped, one half or two thirds as long as 
the ischium. 
The number and arrangement of the gills in the genus Heterocarpus are 
correctly given by Prof. S. I. Smith in Bull. Mus. Comp. Zoél., X. 66, and 
erroneously by Spence Bate in the Report on the Crustacea Macrura of the 
“ Challenger” Expedition, p. 629. 
Heterocarpus hostilis Fax. 
Plate XLI., Fig. 1-1°. 
Bull. Mus. Comp. Zodl., XXTV. 204, 1893. 
The rostrum, measured from the tip to the posterior boundary of the 
orbit, is from one and a half to two and a third times as long as the rest of 
the carapace ; its basal fourth is nearly horizontal, while the remaining por- 
22°; it is armed with seven or eight 
tion is bent up at an angle of about 
teeth above, nine to fourteen below. The dorsal carina of the rostrum 
extends back on the median line of the carapace nearly to the hind border 
of the carapace. There is but one tooth on this carina posterior to the base 
of the rostrum, and that is on the gastric region. 
On each side of the carapace there are two lateral carine. The upper 
* Cf Wood-Mason and Alcock in Ann. Mag. Nat. Hist., 6th Ser., IX. 369, Fig. 6, 1892. 
