4 CEYLON PEARL OYSTER REPORT. 



subchelate or not normally chelate in the male. It is, however, prohahle that up to 

 a certain stage the males may not exhibit this distinction. The species referred to 

 the genus by Sars are H. orstedi (Kroyer), //. limicola (Harger), H. tenuis 

 (G. M. Thomson), //. anomalus, Sars. To these Dollfus, in 1897, adds //. algiricus 

 and LI. provincialis, but, upon a comparison of the descriptions and figures of 

 H. algiricus and H. anomalus, there is no character given by which they can be 

 distinguished. H. V. Hodgson ('Nat. Hist, of the "Southern Cross,'" p. 240, 1902) 

 remarks that but for the structure of the uropods he would have placed his own 

 Paratanais antarctica and Beddard's P. dimorphus in Sars' genus Heterotanais. 



The sjjecies now offered as an additional member of the genus labours under the 

 considerable disadvantage of not being represented by any adult male specimen, 

 apart from which it is not easy to say whether junior or female specimens should be 

 allotted to Heterotanais or Leptochelia. As will be seen by the description, if the 

 minute character of the maxillary palp can be trusted, the species belongs to 

 Heterotanais. As the first gnathopods are remarkably stout, one may be glad to 

 rescue it from a genus like Leptochelia that derives its name from the slenderness of 

 those appendages. 



Heterotanais crassicornis, n. sp. Plate I. (A). 



In the cephalothorax the line of junction between the head and the first perseon 

 segment is slightly indicated. The antepenultimate and penultimate segments of 

 the perseon are the longest. The first five segments of the pleon are subequal, the 

 telsonic segment not elongate. 



The eyes are socketed, at apex in dorsal view apparently, but not really, acute, 

 lenses about 12 in number. 



First antennae : first joint unusually stout, not twice as long as broad, more than 

 twice as long as the second ; third not longer than the second, very narrow, tapering, 

 with three setae, one of which is, perhaps, attached to a scarcely perceptible flagellar 

 joint. 



Second antennas shorter and much narrower than the first, second joint the widest, 

 fourth the longest, but not very long ; a minute flagellar joint is tipped with a very 

 long seta. 



Mandibles nearly as figured by Sars (' Crustacea of Norway,' pi. 6) for H orstedi, 

 but on the left mandible the cutting edge and accessory plate are far less distinctly 

 denticulate, and on the right the cutting edge shows a little tooth, the serration of 

 the upper border being barely perceptible. There is no accessory plate on the right, 

 and on both mandibles the molar is very prominent, as in the species described by 

 Sars. 



The first maxilla has the palp terminated by one seta, in accordance with the 

 generic character given by Sars, whereas in the female of Leptochelia this organ is 

 tipped with two setae. 



