A REVISION OF THE BRITISH IDOTEID^. 751 



(1) Synisoma lancifer (Leach, MSS.).* (PL XI, figs. 115-128.) 



Leptosoma lancifer, Le>ich, MSS. in Brit. Mas. 



Llotea appemliculata, Bate and Westvvood (nee Risso), Brit. Sessile-eyed Crust., 1867, ii, p. 396, figs. 

 Stenosoma lancifer, Dollfus, Feuille desjeunes Nat., 1895, p. 5, fig. 13. 



Stenosoma laitciferum, Norman, Ann. and Mag. Nat. Hist., 1904 (s. 7), xiv, p. 444; Tattersall, Nord. 

 Plank., 1911, p. 230, fig. 118. 



Body oblong, widest at the third mesosomatic segment, with well-marked dorsal 

 keel. Cephalon (fig. 115) wider than long, and wider anteriorly than posteriorly, 

 anterior margin produced in the median line as a depressed sharp point, lateral lobes 

 well developed, sinuous in front of the posterior margin. Eyes moderate in size, 

 situated dorso-laterally. Antennulse (fig. 116) with first joint expanded. Antennae 

 (figs. 117 and 118) fairly stout, first joint short, second the largest, third and fourth 

 subequal, fourth about the length of the first ; flagellum with sixteen joints, 1 to 

 6 cubical, remainder elongated, terminal style short and conical. First maxillae 

 (fig. 119), outer lobe terminating in five stout curved spines and six inner ones, of 

 which two are toothed ; inner lobe terminally rounded, with three long setose spines 

 and a small spine on the outer anterior border of the lobe. The segments of the 

 mesosome (fig. 126) slope from a strong dorsal keel, third segment the widest and 

 longest, gradually becoming smaller anteriorly and posteriorly ; pleural plates small, 

 that of the first segment truncate anteriorly. Coxal plates occupying the anterior 

 half of segments 2 and 3, slightly more of 4, 5, and 6, and nearly the whole 

 of the seventh. Maxillipedes (fig. 120) broad and stout, basal plate medium 

 size, epipodite elongated, narrowing anteriorly, distal inner lobe very wide, with 

 marginal stout spines and setose spines distally (fig. 121). Thoracic appendages 

 (figs. 122-125) somewhat slender, sparsely setose. Metasome (fig. 127) composed of 

 a single segment, with lateral sutures anteriorly indicating three coalesced segments, 

 lateral margins almost straight anteriorly, expanding towards the posterior end and 

 rounded, terminating in a drawn-out rounded process. Uropoda (fig. 128) flattened, 

 endopodite triangular in shape, short setose, style. 

 Length of c? 22"5 mm. 

 Colour (in alcohol) yellowish-brown. 



Geographical Distribution. — South and south-west coast of England (Norman 

 and Stebbing) ; Channel Isles (Koehler) ; also west coast of France (Dollfus) ; 

 Mediterranean (Stephensen). 



I have to thank Dr E. J. Allen, F.R.S., for kindly sending me for examination 

 very fine examples from Wembury Bay and Looe Island. 



Remarks. — This handsome species is easily separated from any of its allies by the 

 prominent keel in adult specimens, and the form of the terminal segment. 



Stephensen's (73) 8. appendiculatum (Risso), 1826, is the S. acuminata of 



♦ As the International Rules of Zoological Nomenclature (1905) prohibit the use of an " unpublished" name, it 

 might be advisable to adopt Dollfds as the authority. 



