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



occasionally carried into the outer channel, and of at least one hydroid washed into 



the main area on drifting weed. To the second category belong several hydroids 



that are able to establish themselves in the salt-water season in the outer channel 



but perish in the summer floods; while to the third must be assigned all the 



Actiniaria, the one Alcyonarian, the one Scyphomedusa and at least two hydroids. 



The number of species that may be tabulated under each of the three headings is as 



follows : — 



Casual visitors . . . . 4 



Periodic immigrants . . . . 3 



Permanent inhabitants . . 9 



Total . . 16 



The casual visitors include one Narcomedusa, one Siphonophoran and two 

 Calyptoblastic Hydrozoa, one of which is represented by the medusoid generation 

 only ; the periodic immigrants consists of one Gymnoblastic and one Calyptoblastic 

 hydroid, with a medusa that may be no more than the fertile generation of the 

 latter; while as permanent residents may be classed five Actiniaria, one Alcyonarian, 

 one Scyphomedusa and two Gymnoblastic hydroids. 



ACTINIARIA. 



(Plate vi (in part), plates vii, viia). 



The Actiniaria of the Chilka Lake belong to three families, five genera and five 

 species. The three families are the Actiniidae, the Sagartiidae and the Edwardsiidae. 

 The first is represented by a single new species of the genus Gyrostoma, the second 

 by two species each of which is placed in a new genus, and the last by new species of 

 Halianthus and Edwardsia. With one exception (that of a Sagartiid previously 

 found in the Gangetic delta) all the species are here described or named for the first 

 time — a fact that is not surprising in view of our present ignorance of the actinian 

 fauna of the Bay of Bengal L and of the estuaries and lagoons connected therewith. 



From a geographical point of view the most interesting feature of the Chilka 

 species is the occurrence among them of Edwardsia and Halianthus , genera known 

 from both northern and southern regions but apparently represented but poorly in 

 the Tropics. 



Biologically the most important forms are those here accepted as the types of 

 new genera of Sagartiidae. Their significance is discussed at some length on pp. 72-76, 

 postea. The apparent effect of the irruption of fresh water into the lake on the 

 species of Halianthus is another interesting feature of the fauna (see p. 91), and may 



1 The only papers on the sea-anemones of the Bay of Bengal that I can trace are those by Alcock in 

 the Journal of the Asiatic Society of Bengal (vol. liXU, part 2, pp. 151 and 169 : 1893), and by Haddon 

 in the Journal of the Linnean Society (Zool., vol. XXI, p. 247: 1888). These papers deal with a few 

 species only. 



