70 Memoirs of the Indian Museum. [Vol. V, 



be compared with that noted in greater detail in the case of the medusa Acromitus 

 rabanchatu (seep. 101); generally speaking , this change in environment seems in both 

 cases to induce a period of physiological quiescence accompanied by a shrinkage of 

 the mesogloea and is probably fatal to a large number of individuals, though not to 

 the species as a whole. 



With my account of the Chilka species I have included a description of a new 

 Gangetic anemone co-generic with one of the former, and also some notes on another 

 Gangetic species that has long been known but is of particular interest in reference 

 to the question of the origin of the fauna of brackish water. These Gangetic species 

 are Phytocoetes gangeticus , sp. nov. and Metridium schillerianum (Stoliczka). 



Family ACTINIIDAE. 



Genus Gyrostoma, Kwietniewski. 



1900. Gyrostoma, Carlgren, Mitt. Naturh. Mus. Hamburg, XVII, p. 55. 

 1905. ,, McMurrich, Zool. Jahrb., Suppl. VI (in), p. 226. 



The only representatives of the Actiniidae found in the Chilka Lake belongs 

 to the genus Gyrostoma as redefined by the authors cited. The genus is represented 

 in all the warmer seas and species have been described from East Africa, South 

 Australia, Torres Straits and the West Indies. 



Gyrostoma glaucum, sp. nov. 

 (Plate viia, fig. 1.) 



In life the animal is of an almost uniform glaucous green colour, but in some 

 individuals there are darker V-shaped cross-bars on the upper surface of the tenta- 

 cles. The column is slender and more or less vase-shaped, much longer than broad 

 when fully extended. The external surface is smooth' to the naked eye, except when 

 the circular muscle is strongly contracted, but is covered with scattered microscopic 

 prominences provided with nematocysts. The contracted muscles are visible as 

 distinct annuli which, in preserved specimens, are more opaque than the expanded 

 parts of the column. 



The oral disk is rather narrow, circular in outline, flat but ridged and grooved 

 radially. The mouth, which is provided with not very prominent lips, is almost 

 linear and occupies about two-thirds of the circle in its longer axis. The tentacles 

 are moderately long and slender ; when fully expanded they are pointed, but even a 

 slight contraction produces a faint ovoid swelling of the tips due to a greater thick- 

 ness of the wall (mainly the ectoderm) in this region. The outer circle consists of 

 about 24 tentacles distinctly longer and stouter than any of the others Within 

 this circle there are four others, but neither the number nor the arrangement is at all 

 regular. Some of the tentacles of the innermost circle, though smaller than the 

 outermost ones, are larger than the majority. These are often thrust into the 

 mouth. 



The basal disk, though small and not extending beyond the margin of the column, 



