160 CEYLON PEARL OYSTER REPORT. 



slight in themselves, and in the light of Ceylon specimens of the former species would 

 appear to almost reach vanishing point 



The eye in the Ceylon examples has the sensory papilla well developed, while the 

 fourth pair of pleopods does not appear to differ from those of typical specimens of 

 N. bipes. N. bipes in one or other of its varieties is a very widely distributed form 

 in the northern hemisphere. Since the examples noted by Stubbing from Sandal 

 Bay, Lifu, and New Britain are more properly, according to Thiele, referable to 

 N. longicornis, Ceylon is the southernmost point from which N. bipes has as yet been 

 recorded. 



II. SCHIZOPODA. 



Family : EUPHAUSIIDjE. 



Euphausia mutica, Hansen (1905). 

 E. pellucida (pars), Sars (1885). 

 Localities : 



Indian Ocean, south of Sokotra, surface tow-net. Three specimens of 10 millims. ; 

 and five, 6 millims and under. 



Indian Ocean, between Sokotra and the Laccadives, surface tow-net. Forty, 5 to 

 15 millims. 



Indian Ocean, between the Laccadives and Ceylon, surface tow-net. Two, 

 11 millims. 



This species was not actually met with in Ceylon waters, but was captured on the 

 outward journey there by means of tow-nets. All the specimens were taken at the 

 surface in crossing the Indian Ocean from Sokotra to Ceylon. 



This species has only recently been founded by Hansen for specimens formerly 

 referred by Sars to E. pellucida, Dana, in which he also included E. mulleri, Glaus, 

 and E. bidentata (M. Sars), as synonyms. Hansen (1905), however, rejects 

 E. pellucida, Dana, as unrecognisable from Dana's descriptions and figures, and makes 

 E. mulleri the type of the genus, with E. bidentata as a synonym. From E. mulleri, 

 E. mutica is chiefly distinguished by having the leaflet on the basal joint of the 

 antennular peduncle bidigitate instead of multidigitate. This latter character is also 

 shared by E. recurva, Hansen, and E. brevis, Hansen. E. mutica, E. recurva, and 

 E. brevis, which all have two latei-al denticles on the carapace, are separated from 

 each other, by Hansen, on the characters of the armature of the second joint of the 

 antennular peduncle and the shape and direction of the antennular leaflet. 



Small examples of E. ynutica in this collection, 5 millims. in length, while in other 

 respects agreeing fairly well with larger examples, only possessed a single lateral 

 denticle on the carapace. This is quite in accordance with the fact that the second 

 denticle is of late appearance, and Saks (1885), moreover, describes and figures a 

 young Euphausian, 7 millims. long, which he refers to E. pellucida, and which has 

 the second denticle on the carapace still undeveloped. 



