208 CEYLON PEARL OYSTER REPORT. 



proportions. The head and free thorax segments are about the same, but the genital 

 segment is relatively longer and narrower, being nearly half the entire length. 



The posterior processes are only one-third as long as in the female, and are spathu- 

 late, being somewhat enlarged and strongly flattened at the tips. Their width at 

 the tip is three- fifths of their length, while in the female it is less than one-seventh. 

 The abdomen lacks the posterior processes, and is nearly hemispherical in shape ; the 

 anal papillae are relatively larger, and their setae, also non -plumose, a trifle longer. 



Colour the same, except that there are no pigment spots on the posterior processes, 

 and there are two narrow lines of pigment parallel to the sides of the genital 

 segment in place of the wide broken lines of eggs seen in the female. 



Total length 1'6 millims., length of head 0'35 millim., length of genital segment 

 0*71 millim., length of posterior processes 0'35 millim., width of genital segment 

 0'3 millim. 



This species was founded by KROYER upon a single female obtained by exchange 

 from the Vienna Museum. And KROYER himself states that this specimen was 

 imperfect, so that the description given was necessarily incomplete. This original 

 type specimen was obtained from a species of Holacanthus (Tetrodon) taken in the 

 Indian Ocean. 



The present lot of material is from the same region and was found on the same 

 genus of fish (Tetrodon) whether upon the same species or not, is impossible to tell, 

 since KROYER does not name the species. The specimens include some twenty 

 females and two males, nearly all of which are in excellent condition. We are 

 thus justified in supplementing KROYER'S description, and in presenting a complete 

 account of both sexes with accurate figures. A genus diagnosis is also here given 

 for the first time (p. 206). 



