Hydrozoa and Ctenophora. 113 
The medusa of this species was abundant in the outer channel of the Tale Sap, 
with Liriope rosacea, in January 1916, and badly preserved colonies of a minute 
hydroid that is probably of the same species were found on the stems of colonies of 
Bimeria from off Koh Yaw when the latter were examined in Calcutta. Many of the 
medusae were sexually mature. 
The medusa and hydroid appeared again in July, 1916 in the canal at Calcutta 
in which they were found in 1915 (see lyloyd and Annandale, 1916). Fuller inquiries 
seem to indicate that they do so about the same time every year, shortly after the 
opening of certain locks that allow water from the outer canal system connected with 
the Mutlah River, and so with the sea, to enter. They disappear as the water be- 
comes fresh or nearly fresh with the fall of the rains, being apparently unable to live 
in water below or much below 1006 in specific gravity (corrected to a standard tem- 
perature of I5°C). 
The species is evidently common in the Bay of Bengal, round the coasts of 
Ceylon and in the Gulf of Siam. 
Order TRACHY MEDUSAE . 
Family OLINDIADIDAE. 
1910. Olindiadae, Mayer, Medusae of the World II, p. 340. 
Subfamily Petasinae. 
1910. Petasinae, Mayer, op. cit., p. 361. 
As it seems to be impossible to recognize any species of Petasus, the name of the 
subfamily may have to be changed, but its limits are at present so uncertain that 
it is best to regard it as a provisional group for which the name adopted in Mayer's 
standard work on the medusae may be used conveniently. 
The genera included provisionally are Petasus {?), Aglauropsts, Craspedacustes 
{= Limnacodium) , Microhydra, Gossea, Maeotias and the new genus here described 
under the name Asenaihia. It is not improbable, however, that Craspedacustes 
and Microhydra are generically identical, while Asenathia may be the medusoid 
generation of the hydroid Annulella, whose name in that case has clear priority. 
Petasus, Aglauropsts (which is still known but imperfectly in the adult state) and 
Gossea are marine genera, t*he development of which is quite unknown, and Gossea, 
the only one of the three of which the generic diagnosis is satisfactorily established , 
differs very considerably in general facies and in the arrangement of its tentacles 
from Craspedacustes, the medusa of Microhydra, Maeotias or Asenathia. These four 
genera live in fresh or brackish water. 
The new genus is nearer to Maeotias ' than to any other, but differs in the struc- 
ture of its gonads and sense-organs, so far as it is possible to base a dogmatic state- 
ment on the brief and incomplete description supplied by the author of Maeotias. 
' Ostrooumofi, Zool. Am. XIX, p. 30 (1896) and Bull. Acad. Imp. Set. St. PStersbourg (5) IV, p. 402, pi. i, figs, i, 
3 (1896) (in Russian). 
