154 STALK-EYED CRUSTACEA. 
below. The carina on the third abdominal segment is not broken into two 
parts (except in one specimen), and is armed with only a single spine, at the 
posterior end. This carina is fluted above, as in H. hostilis, from its anterior 
end to a point corresponding with the position of the anterior spine in the 
adult Z. hostils. Iam inclined to consider these specimens as young stages 
of H. hostilis, especially since in one of those from Station 3363 the carina of 
the third abdominal segment, although not two-spined, is nevertheless cut by 
a notch into an anterior and a posterior section. 
Heterocarpus affinis Fax. 
Plate XL., Fig. 2, 2", 2°; Plate XLI., Fig. 3, 3%. 
Bull. Mus. Comp. Zo6l., XXIV. 204, 1893. 
This species is closely allied to the preceding (ZH. hostilis), from which 
(comparing specimens of the same sex) it differs in the following particu- 
lars: the rostrum is much shorter in proportion to the length of the cara- 
pace ; measured from the tip to the posterior limit of the orbit it about 
equals the rest of the carapace in length in some specimens, while in others 
it is only two thirds as long. ‘There are, moreover, fewer teeth on its 
dorsal margin (five or six), the number of teeth on its ventral margin vary- 
ing from six to ten. The median dorsal line of the carapace is more con- 
vex, and is armed, posteriorly to the base of the rostrum, with two acute 
teeth, whereas in #. hostilis there is but one tooth on this portion of the 
carapace, except in a few abnormal individuals. 
It is also nearly related to H. dorsahs Bate, collected off Banda Island by 
the “ Challenger,” but differs from that species in having a shorter rostrum, 
and two median teeth on the third abdominal segment. 
The exopods of the third maxillipeds are the same size as in ZZ. hostilis, 
whereas in H. dorsalis, according to Bate, they are reduced to a mere 
tubercle. 
HT. affiinis and H. hostilis belong to different geographical areas, as will be 
seen by inspection of the stations at which the two species were procured. 
H. affinis is the more northerly form, from the coast of Mexico (off Acapulco 
and Cape Corrientes), while HZ. hostilis comes from the region about the Gulf 
of Panama. 
Dimensions of a female specimen: length, 153 mm.; length of carapace, 
including rostrum, 76 mm.; length of rostrum, 35 mm. ; length of antennal 
scale, 23 mm.; length of telson, 23.5 mm. 
