270 THE VOYAGE OF H.M.S. CHALLENGES. 



Penseus tenellus, n. sp. 



Animal slender and smooth. Eostrum slightly elevated above the dorsal surface, 

 about one-half the length of the carapace, and armed with seven teeth anterior to the 

 frontal margin, which is furnished with a rather large first antennal tooth, and a small 

 one at the fronto-lateral angle. There is one also on the hepatic region. The rest of the 

 animal is smooth, excepting on the dorsal surface, where there is a small carina that 

 commences on the fourth somite and terminates in a small tooth at the extremity of the 

 sixth. 



The telson is short, tapering, free from armature, and dorsally channelled on the 

 median line. 



The ophthalmopoda are biarticulate, short, the ophthalmus large but not reaching to 

 the extremity of the rostrum. 



The first pair of antennae has the peduncle much longer than the rostrum, and 

 subequal in length to the scaphocerite of the second pair of antennae, which carries a 

 flagellum twice as long as the animal. 



The other appendages, as far as have been examined, offer nothing very striking. 



Length, 35 mm. (1*4 in.), female. 



Habitat.— Station 235, May 17, 1875; lat. 34° 39' N., long. 135° 14' E.; Bay of 

 Kobe, Japan; depth, 8 fathoms; bottom, mud. Dredged. 



The body of the animal is slender, but not much laterally compressed, excepting the 

 three posterior somites of the pleon. The carapace is but little more than one-fourth the 

 length of the animal, and is dorsally compressed but not carinated ; the anterior portion 

 projects to a rostrum that is about half the length of the carapace, and is armed with 

 seven small teeth, all in advance of the frontal margin, the largest being in the middle 

 and the smaller at each extremity. The orbital notch is broad, and at the outer canthus 

 projects into a large and well-defined tooth; there is none corresponding with the second 

 pair of antennae, but the fronto-lateral angle is produced to a small point. On the 

 hepatic region is a small well-defined tooth, but there is none on the gastric region. 



The three anterior somites of the pleon are dorsally smooth, but the fourth, fifth, and 

 sixth are carinated and compressed, the posterior terminating in a small tooth. 



The telson is about half the length of the lateral plates of the rhipidura, and gradually 

 tapers to a point, and has no lateral armature, and is dorsally flattened and longitudinally 

 grooved in the median line. 



The peduncle of the ophthalmopod is short. The first joint has a small, round, flat, 

 discoidal plate on its inner distal extremity, but the ophthalmus is large and reniform, 

 reaching nearly to the extremity of the rostrum. 



The first pair of antennae carries a slender prosartema that reaches nearly to the 



