146 BULLETIN 201, UNITE© STATES NATIONAL MUSEUM 



oval in shape, Sy 2 times as long as broad, setose all around, distal part 

 marked off by a distinct suture. 



Maxilla with an exopod but lacking the setiferous expansion on the 

 lobe from the second joint. 



First thoracic limb very stout, endopod (fig. 53, b) as usual in the 

 genus, 6- jointed, last two joints very broad, nail well developed. 



Third to the eighth thoracic limbs (fig. 53, d) with the carpopro- 

 podus of the endopod divided into two or three subjoints by transverse 

 sutures, nail very long and slender, longer than the distal subjoint of 

 the carpopropodus. 



Telson (fig. 53, /) shorter than the sixth abdominal somite and about 

 five-eighths of the length of the outer uropod, triangular, nearly 

 twice as long as broad at the base, without apical cleft, lateral margins 

 armed throughout their entire length with about 15 to 20 short, stout, 

 blunt spines, more crowded distally. In the specimen figured there 

 are 15 spines on one side and 19 on the other. 



Inner uropod (fig. 53, e) extending about halfway between the apex 

 of the telson and the distal end of the outer uropods, with a row of 

 about 24 spines on the inner margin extending from the statocyst al- 

 most to the distal end. 



Length of adult specimens of both sexes 3 mm. 



Type.— A male, U.S.N.M. No. 81264, St. Croix. 



Occurrence. — Caribbean Sea: St. Croix, 4 fathoms, collected by 

 Dr. T. Mortensen, February 19, 1906, 2 females, 3 males, 3 mm. (type) . 



Remarks. — The specimen described is defective, but the species may 

 be recognized by the combination of characters afforded by the anten- 

 nal scale, uropods, and particularly by the telson with its armature 

 of short blunt spines. 



METAMYSIDOPSIS, new genus 



Similar to Mysidopsis G. O. Sars, except that the maxilla is without 

 an exopod and without the setiferous expansion of the lobe from the 

 second joint. 



Type species. — Mysidopsis munda Zimmer, 1918. 



The establishment of this genus seems justified on the characters 

 mentioned. Zimmer (1918) in the original description of M. munda 

 noted the special characters of the maxilla given above, but while sug- 

 gesting that they may be of more than specific value he did not ac- 

 tually found a new genus for his species. Two further species re- 

 ferred to Mysidopsis, M. elongata Holmes and M. paciftca Zimmer, 

 show the same type of maxilla, and in my view the absence of the exo- 

 pod should be regarded as of generic significance. 



Fifteen species of the genus Mysidopsis have been described and of 

 these it may be definitely stated that the following have an exopod 



