752 DR WALTER E. COLLIN GE. 



Leach, 1815, whilst his S. acuminatum (Leach) — represented by two examples from 

 different localities — is in one case referable to S. capito (Rathke), the other 

 approaching S. lancifer (Leach), but I am inclined to regard it as a distinct species. 



Judging from the material I have examined, I am of opinion that there is a 

 further British species, allied to S. lancifer, in which, however, the metasome has the 

 lateral margins of the terminal segment almost straight, and the posterior margin 

 gradually converging to a blunt point. Stephensen's figure of his S. acuminata 

 (73, p. 15, fig. 5) approaches this very closely. 



2. Synisoma acuminata (Leach). 



Stenosoma acuminatum, Leach, Trans. Linn. Soc. Lond., 1815, xi, p. 366 ; Edinb. Ency., 1833, vii, p. 433. 

 Llotea acuminata, White, List Cnist. Brit. Mus., 1847, p. 95 ; Bate and Westwood, Brit. Sessile-eyed Crust., 



1867, ii, figures on p. 394 ; Miers, Journ. Linn. Soc. Lond., 1881, xvi, p. 59. 

 Stenosoma acuminatum, Dollfus, Feuille des jeunes Nat., 1895, p. 5, fig. 14; Norman, Ann. and May. Nat. 



Hist., 1904 (s. 7), xiv, p. 444; Tattersall, Nord. Plank., 1911, p. 231, fig. 119. 

 Stenosoma appeivliculatum, Stephensen, Rep. Danish Oceanog. Exp., 1915, p. 17, fig. 7. 



I regret that I have not been able to obtain any British examples of this species. 

 The following description is taken from Miers (44), with some slight alterations in 

 the terminology : — 



" Body narrow, elongated, moderately convex, with indications of a longitudinal 

 median dorsal carina. Cephalon with its anterior margin somewhat excavated, and 

 its antero-lateral angles rather prominent. First four segments of the mesosome 

 each widest in the middle, and with their lateral margins (in a dorsal view) more 

 or less angulated ; the posterior segments of the mesosome are widest at or near 

 their postero-lateral angles. Metasome ovate-lanceolate, with the lateral margins 

 at first straight and then curving regularly to the distal extremity, which is subacute 

 or acute, or even acuminated, and with more or less distinct traces of lateral sutures 

 near its base, indicative of two coalescent segments. Eyes small, placed in the 

 middle of the lateral margins. Antennules do not reach the extremity of the ante- 

 penultimate joint of the peduncle of the antennae, with their basal joints moderately 

 dilated. Antennae reaching sometimes to the posterior margin of the sixth meso- 

 somatic segment ; the last two joints of the peduncle slender, subequal, and each 

 longer than the preceding ; fiagellum about nineteen-jointed, and longer than the 

 peduncle. Legs very slender, subequal. The coxal plates (in a dorsal view) are very 

 small, and in the second to fourth segments occupy the middle of the lateral margins ; 

 in the fifth and sixth segments they are placed near to, and in the seventh segment 

 quite at, the postero-lateral angle of the segment ; in the last two segments they are 

 of nearly triangular form. The terminal plates of the uropoda are considerably 

 longer than broad, and rounded at their distal ends. 



" Length of the largest example in the British Museum collection about 1 inch 

 (25 mm.), breadth rather less than \ inch (5 mm.)." 



