CRUSTACEA MALACOSTRACA. III. ^i 



between the somewhat produced angle and the insertion of sixth joint (fig. 3 f), while two spines are 

 found near the inner margin. 



In the female the four anterior thoracic tergites (fig. 3 b) are much shorter at the middle than 

 towards the sides, with the result that broad and proportionately long membranous areas are seen on 

 the dorsal surface between the well chitinized tergites; the first tergite is at the middle much shorter 

 (narrower) than the second, which is scarcely or slightly longer than the third. In the male (fig. 3 a) the 

 first tergite is still narrower at the middle, while the second tergite is long, longer than the third and the 

 fourth combined, and, besides, much vaulted, with three dorsal longitudinal impressions (an aberrant 

 male is mentioned later on). Seen from the side, the dorsal line of the head with the four anterior 

 segments is almost as convex as in M. eximius, and second segment in the male has a curvature of 

 its own.— The three posterior segments slightly to conspicuously less slender than in M. eximius. but 

 otherwise as in this species. 



First pair of thoracic legs (fig. 3 g) have fifth joint about twice as long as deep, with four 

 slender spines on the lower margin; three similar spines are found on the distal part of the lower 

 margin of fourth joint. 



Abdomen conspicuously longer than the three posterior thoracic segments combined, less nar- 

 row than in M. eximius. — The female operculum navicular and keeled nearly as in the last-named 

 form, posteriorly feebly emarginate. The posterior incision in the plate formed by the male uropods 

 of second pair only one-fourth as long as the plate. - - Uropods (fig. 3 m) small, slender, with second 

 joint about twice as long as the first. 



Length of the largest female (without marsupium) 7 mm., of the male 5-3 mm. 



Variation? A single male specimen taken in Davis Strait differs from the typical males in 

 being 6-3 mm. long, in having the posterior section of the body, viz. the three thoracic segments and 

 abdomen, distinctly narrower in proportion to length and distinctly longer in proportion to the whole 

 body; furthermore the second thoracic segment is much shorter, being scarcely longer than the fourth 

 segment, and without the four dorsal tubercles, while the incision in the opercular plate, second pleo- 

 pods, seems to be a little deeper. I am unable to decide with certainty, whether the specimen belongs 

 to another species or the differences observed are due to variation. 



Remarks. The frontal row of setse and other features prove that in referring the typical 

 specimens to Tattersall's species I am correct. His description and figure of the three posterior thoracic 

 segments are certainly wrong, as no transverse articulations are found between them, but extremely 

 curved impressions; when he said "pleopods normal in structure" it shows that he had not examined 

 them in the male. The only difference difficult to explain between his representation and mine is 

 that he figured the fifth joint of first thoracic legs as considerably more slender in proportion to depth 

 than I found it in the same sex; according to his text that joint should, for the rest, be still longer 

 in proportion to sixth joint than his figure shows it to be. 



Occurrence. The male specimen mentioned above under variation? was taken by the 

 "Ingolf" at the following station. 



Davis Strait: Stat. 36: Lat. 6i°5o' N., Long. 56°2i' W., 1435 fath., temp. 1-5°; 1 spec. 



The typical specimens have been gathered by the "Thor" at a single place. 



The Ingolf-Espedition. III. j. 2 1 



