52 BULLETIN OF THE 



rostrum as in R. sculpta, though a little less prominent; and between the lat- 

 eral spines and the curved tip the surface is irregularly corrugated. The 

 inferior edge of the rostrum is grooved, the groove being broadest at the begin- 

 ning of the curved portion, and toward the tip there is in addition a slight 

 median carina. The carinse of the carapax have nearly the same arrangement 

 as in R. sculptat The tubercles of the indistinct dorsal carinse are all very low, 

 obtuse, and punctate, and the space between the carinse unarmed except by a 

 few small tubercles in front. On the lateral lobes of the gastric region the 

 tubercles are all low and obtuse, the anterior being no more prominent than 

 the others. The antennal spine is nearly as in R. sculpta, but the spine of the 

 anterior angle is shorter and stouter than in that species, and directed straight 

 forward as in R. Acjassizii. The lateral carina of the antennal region is con- 

 tinuous and terminates anteriorly in a distinct tooth back of which the edge is 

 obtuse and punctate. Back of the cervical suture, the upper lateral carina is 

 prominent, but the tubercles with which it is surmounted, though more promi- 

 nent than the others on the carapax, are all obtuse and punctate. The middle 

 lateral carina is continuous, broad, and punctate, and the lower carina is very 

 low but well marked by being punctate. The inferior margin of the carapax 

 is carinated as in the other species. 



The eyestalks are very short so as to be almost entirely concealed, and the' 

 eyes themselves relatively about as broad as in the other species, but somewhat 

 flattened anteriorly so that they appear much less prominent, and in the alco- 

 holic .specimen are perfectly white. 



The peduncles of the antennulse reach only to about the middle of the ros- 

 trum and the flagella fall short of its tip, but the proportions of both peduncles 

 and flagella are very nearly as in the other species. The antennal scales 

 scarcely reach to the tips of the peduncles of the antennula;, are ovate, about 

 three fifths as broad as long, broadest distally, and have a very indistinct tooth 

 about the middle of the outer margin which is only obscurely ciliated back of 

 the tooth. 



The external maxillipeds and the first pair of thoracic legs are slightly 

 shorter, reaching scarcely to the tips of the antennal scales, but otherwise as 

 in R. sculpta. The thoracic legs of the second pair are similar to those of 

 R. sculpta, but the right reaches a little beyond the tip of the antennal scale 

 and its carpus has about twenty-one segments ; the left is a little shorter than 

 the right and its carpus has about eighteen segments. The third legs are 

 nearly as in the other species, reach a little beyond the ti])s of the antennal 

 scales, and their dactyli are about a third as long as the propodi and very 

 slender. The fourth and fifth pairs of legs are but very little if at all stouter 

 than the third, the fascicles of setae at the tips of the propodi are nearly as long 

 as the propodi themselves, and the propodi are slightly shorter than in the third 

 pair, strongly compressed as in R. Agassizii, but slender and not expanded at 

 all in the middle. 



The sculpturing of the abdomen resembles that of 7?. sculpta, but the dorsal 

 carina is less prominent and more obtuse, and the tubercles are fewer in num- 



