316 DR. H, J. HANSEN ON THE [NoV. 29, 



following pairs, the lateral portions of which are generally com- 

 pletely covered by the second pair. 



Second pair in the male large ; the major portion of the 

 sympods situated outside and coupled with the first pair. Rami 

 attached to the distal half of the inner margin of the sympod ; 

 endopod strongly geniculate, its distal joint slender, containing 

 an internal cavity and distally produced into a point ; exopod very 

 short, many times shorter than the endopod, two-jointed, narrow, 

 hook-shaped, without setae. 



Third pair in both sexes has the exopods of moderate size, not 

 touching each other in the mesial line, generally completely 

 covered by the first pair (in the female) or by the two anterior 

 pairs (in the male) ; only in the male of a single form their 

 exterior portion is uncovered. 



Fifth pair with only one ramus, in all probability the exopod. 



YII. The Species of the Genus Stenetrium. 



The genus was established in 1881 by A. Haswell on two 

 species, S. armatum Hasw. and S. inerme Hasw. The first- 

 named must be regarded as the type for the genus ; besides it 

 will be proved below that according to Haswell's description and 

 figures of S. inerme this species, in all probability, cannot be 

 referred to the same genus. 



Though I have examined only one of the five species referred to 

 Stenetrium by previous authors, I have deemed it useful to incor- 

 porate them in the analytical key, and to describe them as well as 

 possible, applying some of the characters found in the descriptions 

 of the authors, and adding others drawn from their figures, hoping 

 that these are tolerably correct as to the details in question. It 

 has not been my intention to mention features showing difierences 

 of slight or no value for the determination of the species. 



Conspectus of the Species*. 



A. Basal joint of antennulse, seen from above, 

 anteriorly at tlie outer side produced into an 

 oblong acute process, or at least (in S. has- 

 wellii) with a conspicuous tooth marked off 

 from the oblique front margin by an inden- 

 tation. 

 a. First thoracic legs with the upper distal 

 corner of fifth joint f not produced into a 

 process. 

 cc. Hand of first legs in both sexes conspi- 

 cuously more than f as long as deep 1. S. armatum Hasw. 



/3. Hand of first legs in the male (?) less than 

 •| as long as deep (only one specimen 

 known) 2. S.fractum Oxilion. 



* In the kej' S. inerme Haswell is omitted ; this species is mentioned below after 

 the descriptions of the other forms. 



t First joint of these legs is fused with the thoracic segment ; the following long 

 joint, which apparently is the first, is here and in the sequel regarded as the second,, 

 according to the morphological interpretation of these legs ; in the six other pairs 

 of thoracic legs the first short joint is, as in all Asellota, not fused with the thorax 

 but movable. 



