162 CEYLON PEARL OYSTER REPORT. 



peduncle. It is about four times as long as broad, with its outer margin slightly 

 curved and terminating in a distinct though feeble spine. The apex of the scale 

 is broadly rounded, while its basal spine is short and smooth. 



The mouth parts and thoracic limbs offer no points of special interest. 



The telson, including the subapical spines, is about as long as the last two segments 

 of the pleon combined. It is narrowly lanceolate in shape, with the portion beyond 

 the insertion of the subapical spines suddenly constricted and acutely pointed. Its 

 dorsal surface bears five pairs of dorsal denticles on its distal half. The subapical 

 spines have rather broad insertions and their inner distal edge bears five small 

 denticles. 



The uropods have the plates subequal in length and very slightly shorter than the 

 telson. The inner plate is much narrower than the outer, which terminates in a 

 minute spine on its outer edge. 



Length of the largest specimen 12 millims. 



The numerous specimens in this collection which I refer to this species differ from 

 the descriptions, and figures of SARS in four points, (1) in the presence of a lateral 

 denticle on the carapace, (.2) in the very much more digitate form of the membranous 

 leaflet of the antermules, (3) in the presence of five instead of three pairs of denticles 

 on the telson, (4) in the greater relative development of the uropods. The last 

 three points of difference may be accounted for by the difference in size and age 

 of SARS' specimens and my own. SARS' descriptions and figures were taken from a 

 specimen 7 '5 millims. long, while the above description is of a specimen 12 millims. 

 long. The first of the above-mentioned differences is due to an error on SARS' 

 part. 



The examination of the type of E. latifrons, for which I am greatly indebted to 

 Dr. W. T. CALMAN, reveals the presence of a small but quite distinct spine on the 

 lateral margin of the carapace just in front of the luminous organ of the penultimate 

 thoracic limb. The type specimen, according to information kindly given to me by 

 Dr. CALMAN, is one of those from Port Jackson, Australia, mentioned by SARS in his 

 'Challenger Report,' p. 96, as having come to hand late. It is, therefore, not 'the 

 specimen figured or described. It is not quite as large as some of the Ceylon 

 specimens, but considerably more developed than the one SARS figured. The leaflet 

 on the basal joint of the antennular peduncle of this specimen is divided up distally 

 into nine rather short lappets, being thus intermediate in development between SARS' 

 figure and my own. 



STEBBING (1905), in recording this species from S. Africa, notes the presence of a 

 lateral denticle on his specimens, and is of opinion that it probably becomes obsolete 

 in quite adult examples. 



Euphausia latifrons is the smallest known species of the genus, and is at once 

 distinguished from all other described species by the peculiar form of the rostral 

 projection. 



