1909.] FROM THE BAY OF BISCAY. 871 



The single male specimen taken by the ' Huxley ' measures 

 8"75 mm. and has apparently just undergone ecdysis, the integu- 

 ment being exceedingly thin and transparent and easily crumpled. 

 The whole animal is much more slender and compressed than the 

 Irish specimens, probably owing to its condition ; it diffeis also 

 in having well-marked carinsD on the 7th segment, while all the 

 other segments are smooth, and in the number and proportions 

 of the antennal joints. This latter point is pi^obably due to 

 immaturity, the length of the joints of the peduncle and the 

 number of joints in the flagella increasing with age. 



Integimient (fig. 50). — The whole animal is covered with 

 minute scale-like plates, with pectinate margins. 



Perceon. — In the young from the incubatory pouch, 2*25 and 

 3 mm. long, the perceon is perfectly smooth, the dorsal processes 

 and lateral carinas of the 7th segment being represented l)y 

 mobile sensory setules, each inset in a little depression of the 

 cuticle. The 7th dorsal process appears to develop first, followed 

 by the 1st, 2nd, and 3rd consecutively, then the 6th and 4th, the 

 5th being the smalle.st and the last to arrive. At about 5 mm. 

 length the 7th hump commences as a slight rounding of the 

 margin behind. At 7 mm. it is well developed and elevated as 

 in the adult, and the 1st also can be seen. At 8-9 mm. the 

 hump on the 2nd segment has appeared ; and at 10 mm. the 1st, 

 2nd, 3rd, and 7th are well-marked, and the lateral carinse of the 

 7th segment indicated by a rounding of the margin. In only 

 the largest specimens, 11-13 mm., are all seven humps developed ; 

 lateral carina) ending in denticles. The posterior angles of the 

 hinder segments are produced backwards, those of the 7th acute 

 and slightly serrate. 



S ide-2)lates overlapping considerably. Anterior lobe of the 5t]i 

 broader than posterior ; anterior lobe of 6th very small ; 5th and 

 6th ridged laterally ; in the young from the incubatory pouch the 

 lateral ridges are distinctly though faintly indicated ; 5th, 6th, 

 and 7th serrate behind. 



Pleon. — The posterolateral margins of the fii'st three segments 

 firmly serrate, the serrations turning the corner ; segments 1 and 

 2 more rounded in the female than in the male, the teeth of 

 the lateral carinse and the serrations downcurved ; segment 3 

 rounded quadrate, evenly serrated, the lateial denticles and the 

 12-14 serrations upcurved. The 3rd segment in both male and 

 female carries a row of long, plumose sensory hairs, set just under 

 the projecting tooth of the dorsal carina of the 2nd segment. In 

 the young the dorsal carinas of segments 1-4 are indicated, as 

 also the lateral carinse of the 3rd, and in the place of the denticles 

 which develop later, minute sensory setviles, similar to those of 

 the peraeon, are inset. The apices of the telson and of the uropods 

 are likewise provided with these setules. 



Head about the length of the first two perseonal segments in the 

 female, of the first three in the male ; rostrum broad and deflexed, 

 not quite half the length of the 1st joint of the superior antenna. 



