REPORT ON THE CRUSTACEA MACRURA. 



015 



The rhipidura is well developed and has the telson subequal in length with the lateral 

 plates ; the telson is dorso-laterally armed with four small pairs of spinules. 



Observations. — This species was taken at the same station as the preceding, with which 

 it was associated. It corresponds with it in many points, but differs in the more slender 

 general appearance of the animal, in the slender and feeble character of the armature on 

 the rostrum, and in the absence of any carina-like elevation on the dorsal surface of the 

 carapace posterior to the gastric region ; and in the presence of three pairs of teeth on the 

 ventral surface of the posterior somites of the pereion. 



Hetairus debilis, n. sp. (PL CIX. fig. 4). 



Rostrum about half the length of the carapace ; armed on the dorsal surface of the 

 frontal crest with four small teeth, and without any on the rostrum proper, which 

 terminates in a sharp pointed apex ; under surface slightly broader near the apical 

 extremity and armed with three minute teeth. 



Length, entire (minus telson), 



of carapace, 



of rostrum, 



of pleon (minus telson), 

 of third somite of pleon, 

 of sixth somite of pleon, 

 of telson, 



Habitat— Station 49, May 20, 1873 ; lat. 43° 3' N., long. 03° 39' W.; depth, 85 

 fathoms ; bottom, gravel, stones ; bottom temperature, 35°. Fifteen specimens, the 

 majority of which were young and the sex not readily determined ; of those full grown, 

 two are females and one male. Dredged. 



This species corresponds in many points with the preceding, but has the rostrum 

 shorter and more slender. The upper surface is armed near the base with four small 

 teeth, of which two are posterior to the orbital margin ; nearer the apical extremity there 

 are two small lobes, apparently the rudiments of more perfect teeth ; there are three 

 small teeth on the under surface. The ventral surface of each of the posterior three 

 somites of the pereion is armed with a pair of teeth. 



The rhipidura is broken off. 



This specimen appears to me to form a link in a series by which extreme forms are 

 united, or it may be only a younger form of Hetairus tenuis. 



