535 



The body is exceptionally thin and long. The head together with the 

 neck and rostrum is longer than the pereon and often larger than the 

 pereon and pleon together. The neck is very narrow, of the same length 

 as the central part of the head occupied by the eyes, or very slightly 

 longer. The rostrum is acicular and very long. 



The pereon is just shorter than or equal to the pleon in length. 

 The pereon somites are low, the boundaries between them sometimes 

 not clearly developed. The coxal plates are completely fused with the 

 pereon. The pereopods are thin, relatively short and weakly armed. Pere- 

 opods VII are greatly reduced, sometimes one- to two- segmented; how- 

 ever, this character is variable and there are specimens of the same 

 species, sex, and size in which the degree of reduction of pereopods VII 

 varies significantly — from greatly reduced to completely segmented. 



The urosome is longer than the pleon, with highly elongated and 

 tapered somites and uropods. The endopodites of uropods II-III are fused 

 with the basipodites. The telson may be long, acicular, or relatively short, 

 virgate. It is generally separated from the last urosomite, rarely fused 

 with it. 



Type species: Oxycephalus armatus Milne-Edwards, 1 840. 

 Notes: Representatives of the genus Rhabdosoma appeal" so 

 grotesque, and in some morphological features so far removed from 

 the most "typical" genera of the family Oxycephalidae {Oxycephalus, 

 Streetsia) that Bovallius (1890) and later Stebbing (1895) and Spandl 

 (1927) thought it possible to include them in an independent family 

 (Xiphocephalidae — according to Bovallius, and Rhabdosomidae — other 

 authors). At present, the majority of investigators, following Stephensen 

 (1925a), include the genus Rhabdosoma in the family Oxycephalidae. 

 Stephensen convincingly showed that some characters used by Bovallius 

 and Stebbing to include this genus in an independent family (shape 

 of pereopods VII, separation or fusion of the telson and urosome) are 

 subject to variation, while other characters are simply the result of 

 confusion (absence of brood plates in females), and still others have 

 a very wide range of variation for the family Oxycephalidae, exhibiting 

 its extreme manifestations (strong elongation of the body with tapered 

 rostrum and urosome). 



The genus includes four species. 



KEY TO SPECIES OF GENUS RHABDOSOMA 



1. Body size up to 7-15 cm. Telson pointed at tip, longer than 

 uropods II. Females with five pair gills at base of pereopods II-VI . . 

 2. 



