REPORT ON THE CRUSTACEA MACRURA. 



617 



Chorismus tuber culatus, n. sp. (PI. CX. fig. 2). 



Carapace smooth, anteriorly produced to a long, slightly upturned rostrum, armed on 

 the upper surface near the base with four teeth, and on the under surface with seven ; 

 apex bifid. Frontal margin with a strong first antennal tooth, and a small tooth at the 

 fronto-lateral angle. 



Pleon smooth, except the third somite, which dorsally carries a strong tubercle, hence 

 the specific name. 



The telson is long, tapering, and furnished with two distinct spines on the dorso- 

 lateral margin. 



Habitat.— Station 145a, December 27, 1873; lat. 46° 41' S., long. 38° 10' E.; off 

 Marion Island; depth, 310 fathoms; bottom, volcanic sand. Fifteen specimens, the 

 males appearing to predominate ; none of the females bear ova. Dredged. 



The main interest of this species arises from its external resemblance to the genus 

 Mcrhippolyte, while its branchiae approximate to those of Spirontocaris. 



The mandibles do not exactly correspond with those of either of these two genera, 

 nor does the second pair of gnathopoda, which carries no branch. 



The rostrum is very long, and gradually curves upwards towards the apex, which 

 terminates in a double point. Above the orbit, commencing posteriorly over the gastric 

 region, there are four anteriorly pointed, sharp, low lying teeth, the anterior of which is 

 in advance of the eye, and beyond it the rostrum is smooth to the apex. The lower 

 margin is armed with six or seven teeth, which gradually increase in size and depth 

 posteriorly. The orbit is defined by a small point or tooth at the outer canthus on the 

 inner side of the first antennal tooth. 



The ophthalmopod (fig. 2a) is pear-shaped, being smaller at the base than at the 

 ophthalmus, and attached to the somite by a small but distinct pedicle ; the ophthalmus 

 is hemispherical, and has no distinct ocellus connected with it. 



The first pair of antennae is short, the peduncle reaching a little beyond the extremity 

 of the eyes. The outer and more robust flagellum scarcely reaches to the extremity of 

 the rostrum, and the inner, which is slender and filamentous, reaches a little beyond it. 



The second pair of antennae carries a strong scaphocerite, which is strengthened on 

 the outer margin by a strong ridge, terminating in a sharp-pointed tooth that falls short 



(ZOOL. CHALL. EXP. — PAET LII.- — 1887.) Fff 78 



