XIII. REPORT ON A COLLECTION OF 



FREE-IylVING NEMATODES FROM THE 



CHILKA LAKE ON THE EAST 



COASTOFINDIA. 



By F. H. Stewart, D.Sc. 



[The collection on which t!iis paper is based was made in connection with a 

 zoological survey of the Chilka Lake now being undertaken by zoologists attached 

 to the Indian Museum. The lake is a large lagoon connected with the sea by a 

 narrow mouth and containing water that varies greatly in salinity at different 

 places and at different seasons. Full particulars on this and other points will be 

 given in a later paper — N. Annandale.] 



Distribution of the genera to w^hich the species described 

 in the following report belong. 



(i) Geographical. The four genera Oncholaimus, Dorylai- 

 mus, Monhystera, and Leptosomatum are cosmopolitan. Species 

 of Oncholaimus, Monhystera, and Le/^/oso/vjailwm have been recorded 

 from localities ranging from Scandinavia to the Antarctic, while 

 Dorylaimus also occurs in the five continents and the Pacific 

 islands. 



(2) Habitat. Oncholaimus is almost exclusively a marine 

 genus. The exceptions to this rule recorded up to the present 

 are — 0. rivalis, Leydig, a doubtful Oncholaimus (Lit. i) ; 0. 

 thalassophygas, de Man, which occurs in fresh water and the soil in 

 Holland (Lit. 7) ; 0. indicus v. Linstow, in the brackish water of 

 the Ganges delta. 



Dorylaimus has been recorded only from fresh water and the 

 soil. 



Monhystera is chiefly a freshwater genus. Bastian (Lit. i) 

 describes two species (M. disjuncta and ambigua) from the sea, 

 with a doubt, however, as to whether they should truly be classed 

 in the genus. G. Schneider (Lit. 11) describes two species (M. 

 trabeculosa and hipimctata) from the Baltic. Several species such 

 as M. microphthalma, macrura, and agilis, deMan, inhabit brackish 

 water. 



Leptosomatum is entirel}^ marine. 



Oncholaimus chilkensis, sp. nov. 



(PI. XXX, figs. I — 4; PI. xxxi, figs. 15, 17, 18.) 



Two tubes; (i) Indian Museum No. ZEV. 6237/7. Among 

 filamentous algae at edge of lake : Chilka Lake, Gantasila, Ganjam 

 district, Madras. 19-4-14. Two adult female specimens, mounted 



