MUSEUM OF COMPARATIVE ZOOLOGY, 49 



Length of merus right, 8.4 mm. ; left, 8.7 mm. 



" carpus . . . ... 



" chela 



" third pair of legs .... 



" fifth pair of lega 



" telson 



Station 326, N. Lat. 33° 42' 15", W. Long. 76° 0' 50", 464 fathoms. 



Rhachocaris sculpta, sp. nov. 



Plate V. Fig. 3. Plate VI. Figs. 3 - 3*. 



Female, — This species, though closely resembling the last in structure and 

 general appearance, differs very conspicuously in the ornamentation of the 

 carapax and abdomen, and in the form of the dactyli of the fourth and fifth 

 pairs of thoracic legs. It is distinguished from R. Agassizii at a glance by 

 having the dorsal and upper lateral carince of the carapax only obscurely indi- 

 cated by lines of acute tubercles and the spaces between the carinse tubercu- 

 lous, by having two short spines each side in place of the great lateral spine of 

 the antennal region and a small bidentate tooth in place of the sharp branchial 

 spine of R. Agassizii, and in having three instead of two lateral spines on the 

 epimeron of the fifth somite of the abdomen. 



The postero-lateral angle of the carapax is more prominent and angular than 

 in R. Agassizii, but in other respects the form is very nearly the same. The 

 lateral carinae on the posterior part of the rostrum are not so high, and the two 

 teeth at the base of the rostrum are even smaller than the rostral teeth and are 

 nearly erect. All the carinje of the carapax are much less prominent, so that 

 the carapax is more regularly rounded. The space between the two dorsal 

 carinse is scarcely at all depressed, the transverse sulcus at the cervical suture 

 is not as deep, and there are two lines of small spiniform tubercles extending 

 the whole length of the space, and the dorsal carinse themselves are represented 

 by two similar lines of larger spiniform tubercles with about twelve tubercles 

 in each line, and with an obscure line of minute tubercles just outside of them. 

 Below the dorsal carina and just back of the eye either side, at tlie extreme 

 anterior end of the lateral lobe of the gastric region, there is a very large verti- 

 cally compressed and acute tooth or spine connected with the lateral carina of 

 the rostrum by a low but conspicuous ridge, just back of the base of this tooth 

 there are one or two small spines, and on the rest of the triangular lateral lobe 

 of the gastric region between these and the cervical suture there are approxi- 

 mately twelve spines or tubercles, of which those in the middle of the lobe are 

 larger than the others. Of the three spines of the antennal region, the antennal 

 itself is longer than in R. Agassizii, much stouter, considerably expanded at the 

 base and directed strongly outward as well as forward and upward ; the spine 

 of the antero-lateral margin is stouter and directed more outward ; while back 

 of and between these spines there are two relatively small acute teeth directed 



VOL. X. — NO. 1. 4 



