724 THE VOYAGE OF H.M.S. CHALLENGER. 



and terminating in a simple dactylos. Fourth pair similar to the third. Fifth pair a 

 little more robust. 



Pleopoda biramose, the ultimate pair being a little longer than the telson, and having 

 the outer branch furnished with a diaeresis. 



Geographical Distribution. — Only two species of this genus are known ; they were 

 both obtained at more than two miles in depth in mid ocean, one in the Pacific, and the 

 other in the Atlantic. 



Bentheocaris exuens, n. sp. (PI. CXXIII. fig. 3). 



Animal slender, having the dermal tissue soft and membranous. Carapace dorsally 

 flat and smooth, except over the frontal region, where it is armed with a few small 

 teeth that are continued on the rostrum, which is bent downwards and terminates in a 

 fine, pointed tooth. 



Pleon long and subequal in depth with the carapace. First somite short, second a 

 little longer, and both dorsally smooth ; third quite twice the length of the second, and 

 terminating in a horizontal tooth in the median line of the dorsal surface ; fourth and 

 fifth somites similarly armed, but the tooth is smaller on each ; sixth somite about 

 twice the length of the fifth, and armed with a small tooth or spine. 



Telson subequal in length with the sixth somite, and terminating in two or three 

 small hairs. 



Habitat— Station 285, October 14, 1875; lat. 32° 36' S., long. 137° 43' W.; South 

 Pacific Ocean ; depth, 2357 fathoms ; bottom, red clay ; bottom temperature, 35°. One 

 specimen in the tow-net attached to the trawl. 



The species resembles many of the deep-sea forms in being soft and membranous, 

 and has a slender appearance owing to the shortness and want of depth of the pereion. 

 The carapace is about one-third of the animal in length ; its surface is smooth generally, 

 and it is dorsally flat and anteriorly produced to a short, downwardly curved rostrum 

 (fig. 3c), that is about one-fifth the length of the carapace, and armed on the dorsal 

 surface with six teeth, those situated on the frontal region being short, while those 

 towards the extremity of the rostrum are long and slender. The frontal margin of the 

 carapace has an excavation above the orbit and beneath the rostrum, and a slight 

 excavation below this represents the orbit, which is defined by a small point or pro- 



