74 CRUSTACEA MALACOSTRACA. III. 



anterior pairs of legs subsimilar, in the place of the uropods, etc. Pseudomesus is perhaps more allied 

 to Nannoniscus than to any other genus, but yet differs in important features. 

 Only a single species is known. 



45. Pseudomesus brevicornis n. sp. 

 (PI. IV, figs. 5 a 5 g). 



Female. Body scarcely six times as long as broad; second segment and abdomen subequal 

 in breadth and broader than the other parts. Head, seen from above (fig. 5 b), a little longer than 

 broad; seen from the side very deep (fig. 53). - The antennulas occupy a lateral position and consist 

 of five joints (fig. 5 c); second joint considerably longer than the three distal joints combined, and with 

 a couple of long terminal setae; third joint a little longer than the fourth, while the fifth is very small 

 with two long setae. 



The thoracic legs show some particulars not mentioned above. First pair have three spines on 

 the lower margin of fifth joint, each spine with a seta somewhat from the end, and in the intervals 

 between the spines a long, low and thin lamella with numerous tiny hairs on the margin (fig. 5f, ); 

 a similar lamella is also found on fourth joint; sixth joint without spines. Second pair have four 

 spines and the same number of lamellae on fifth joint, two spines on the sixth joint. (Third pair want- 

 ing). Fourth pair with a single spine on fifth joint, three spines and two lamellae on the sixth. The 

 three posterior pairs have a peculiar, slender, triangular process on the posterior margin of third joint 

 rather near the base, and a single conspicuous seta on the lower side of fifth joint a little from the end. 



Abdomen somewhat longer than the two posterior thoracic segments combined, somewhat longer 

 than broad and rather highly vaulted. - - Operculum (fig. 5'g) somewhat longer than broad, with a 

 short proximal part much vaulted (fig. 53); the posterior half has the margin nearly semicircular. - 

 The uropods as mentioned above; first joint thicker and much longer than the second. 



Length of two females with marsupium 3-2 and 2 - 8 mm. 



Remarks. As only a single species is known, some of the minor features mentioned in the 

 description of the genus may be only of specific value. Unfortunately the male is unknown. -- P. 

 brevicornis differs very much from all other forms of Asellota hitherto known; it may be said to have 

 some similarity in general aspect to Thambema amicorum Stebb., but differs in mouth-parts, thoracic 

 segments, legs, etc. 



Occurrence. Taken by the "Ingolf at a single station in the cold area. 



North of Iceland: Stat. 102: Lat. 6623' N., Long. io26' W., 750 fath., temp, -f- 0-9; z l / 2 spec. 



Group VII. Macrostylini. 



Founded on a single very peculiar genus. In order to avoid reiteration it may suffice to 

 refer to the following treatment of the genus. 



