y 6 Memoirs of the Indian Museum. [Vol. V, 



has become structurally adapted, without losing certain essentially 

 Metridiine characters, to life as a burrower in mud. 



(6) The species of Phytocoetes found in the Chilka Lake is distinct from that 



found at Port Canning, while the Pelocoetes is specifically identical in 

 the two localities. 



(7) Metridium schillerianum does not occur in the Chilka Lake. 



The following key to the species of Metridiinae that occur in brackish water in 

 India may be useful to naturalists in this country : — 



1. Basal disk large and strongly adherent; column in nor- 



mal state no longer than wide. 

 Tentacles about 168, arranged round the disk in 5 



circles . . . . . . . . Metridium schillerianum. 



2. Basal disk reduced, feebly adherent; column elongated. 



A. Tentacles arranged in one circle of 12 and in 12 



groups of 5 to 9 each, 72 to 120 in all . . Pelocoetes exul. 



B. Tentacles less than 60, arranged in uninterrupted 



circles, 

 i. Tentacles 21-24 ; anterior sphincter well 

 differentiated, visible on the surface as a 

 prominent ring . . . . . . Phytocoetes' chilkaeus. 



ii. Tentacles about 36 ; anterior sphincter prac- 

 tically absent, not visible on the surface . . Phytocoetes gangeticus. 



Genus Metridium, Oken. 

 1905. Metridium, McMurrich, Zool. Jarhb., Suppl. VI, (III), p. 276. 



Metridium schillerianum (Stoliczka). 

 (Plate vii, fig. 1.) 



1868. Sagartia schilleriana , Stoliczka, Proc. As. Soc. Bengal, pp. 174,263. 



1869. Sagartia schilleriana , id., Journ. As. Soc. Bengal XXXVIII (2), p. 31, 



pis. x, xi. 

 1882. Sagartia schilleriana, Hertwig, "Challenger" Rep. Zool. VI, Actiniaria, 



p. 71. 

 1907. Metridium schillerianum (typical form), Annandale,, Rec. Ind. Mus. I, 



p. 45, pi. iii, figs. 1, 2, 5. 



My description of "the typical form" of this species (1907) should render the 

 identification of specimens a comparatively easy matter, but there are one or two 

 points both in its anatomy and its ecology on which further notes may be useful. 



Strictly speaking it is perhaps incorrect to talk of the existence of a sphincter 

 in M. schillerianum, for all that can be said is that the circular muscle of the column 

 is thrown into more conspicuous folds a short distance below the disk than elsewhere, 



