62 CRUSTACEA MALACOSTRACA. III. 



Thorax with a pair of lateral processes on first segment and none on the others. These pro- 

 cesses (figs. 2 a and 2 b) are very much shorter than in H. quadrispinosus, being of moderate length 

 and thickness, each conspicuously less than half as long as the breadth of the segment, directed much 

 upwards and outwards and somewhat forwards. The three following segments without any vestige of 

 processes. Fourth segment about as in H. quadrispinosus. Fifth segment extremely elongate, slightly 

 more than half as long as the entire animal, and besides extremely slender, being about fourteen times 

 as long as broad somewhat before the middle ; its widened terminal part a little narrower than second 

 segment Seventh segment in my specimen unusually small (fig. 2 d) and without legs (fig. 2e); these 

 features show that the specimen must be rather far from adult. 



First pair of thoracic legs (fig. 2 c) in the main as in H. quadrispinosus, but fifth joint has a 

 single very long, thin spine and two short spines, and sixth joint a single spine on the lower margin. 

 The other legs, as far as preserved, nearly as in H. quadrispinosus; second joints of fourth and fifth 

 pairs, when directed respectively backwards and forwards, do not quite reach one another. 



Abdomen (figs. 2 a, 2 d and 2 e) triangular in aspect, because, having the lateral margins con- 

 spicuously sinuate, it increases somewhat irregularly in breadth from the base to the posterior margin ; 

 each postero-lateral angle is produced in a conical process directed outwards and backwards, slightly 

 longer than the uropods, conical with the end obtuse. The posterior margin between these processes 

 is, taken as a whole, moderately convex, but a little more than its median third protrudes further 

 backwards and has its margin semicircular; this protruding part is the terminal portion of the rather 

 broad longitudinal median area of the surface (fig. 2 d). - - The median lamella of the operculum (fig. 

 2 e) is towards the base distinctly narrower than in H. quadrispinosus, but otherwise of the same shape. 

 - The uropods about twice as long as in that species. 



Length of the specimen described 4-8 mm. 



Remarks. This extremely slender species is instantly separated from the other forms by having 

 only a moderately large pair of processes on first segment and none on the other thoracic segments; 

 besides, the shape of abdomen affords excellent characters, as it differs much from the other forms 

 excepting H. insignis. As the specimen described has seventh pair of thoracic legs totally wanting it 

 must be very far from adult; I suppose that really full-grown males may measure 9 12 mm. in length. 



The type has been taken in the warm area. From a station in the cold area I have a male, 

 which unfortunately is very mutilated, as two anterior segments with head are lost; this specimen is 

 somewhat smaller, with fifth segment, as consequently might be expected, distinctly less slender, only 

 ten times as long as its breadth before the middle, but in all other respects, especially the small seventh 

 segment and the shape of the abdomen, this specimen agrees so completely with the type, that I must 

 refer it to this species. As H. quadrispinosus has been taken some times in both areas, the occurrence 

 of H. angustus is less astonishing. 



Occurrence. Taken by the "Ingolf" at two stations. 



South of Denmark Strait: Stat 18: Lat. 6i44' N., Long. 3O29' W., 1135 fath., temp. 3-0; i spec. 



(c?, type). 



North of Iceland: StaL 125: Lat 68o8' N., Long. i6o2' W., 729 fath., temp. -^0-8; i spec, (mu- 

 tilated c?). 



