1915. ] T. SOUTHWELL: Indian Parasites of Fish, 325 
It is significant that the parasites, both at Cossim Bazar and 
Siripur, only attacked Labeo rohita, although other species of fish, 
such as Catla buchanani and Cirrhina mirgala, were living in the 
same tank at Cossim Bazar, and in the next tanks at Siripur. 
The mortality amongst tank fish in particular, due to the pre- 
sence of this parasite, is, in all probability, fairly extensive in 
Bengal. In nature, however, the parasites are rarely dangerous. 
The practice of stocking tanks with fish—so prevalent in Bengal— 
undoubtedly favours conditions under which the parasite thrives. 
It is known that in Europe the parasites themselves are eagerly 
devoured by roach, dace and bream. The presence of such fish 
therefore tends to check the distribution of the parasite and thus 
to protect other fish from their attacks. It seems possible that in 
our tanks at Siripur, the frogs, when allowed to enter, also de: 
voured the parasites, but no direct observations were made in this 
connection, and hence we have no certainty that such was really 
the case. 
The family Argulidae, Muller, belongs to the sub-order 
Branchiura, Thorell, and to the order Copepoda, Muller. It con- 
tains three genera viz. Argulus, Chonopeltits and Dolops. In the 
former two genera the first maxillipeds are modified into sucking 
discs and in the latter genus sucking discs are absent. The genus 
Argulus contains about thirty-two species of which only three are 
European, the rest being found in American waters. The majority 
of the forms are marine. The various species exhibit but little 
trace of degeneration, a circumstance one would expect consider- 
ing the alternation which exists between temporary parasitism 
and a free life. The males differ but slightly from the females but 
are considerably smaller. 
Our specimens, of which we have over 200, are small, the ex- 
treme length of the largest female was 3'2 mm. and the greatest 
breadth was 2°72 mm. The carapace is elliptical. The posterior 
sinus extends nearly half-way up the length of the carapace. The 
abdomen is almost square and about + the length of the body. 
The suckers are small, placed quite anteriorly and well separated 
from each other. Their diameter is almost -¢ mm. The basal 
plate of the posterior maxillipeds is triangular in shape with 
three well defined, sharp, rectangular teeth. All the swimming 
legs extend well beyond the edge of the carapace. In the male 
the abdomen is much longer and narrower than in the female, and 
the sinus is narrow, sharply cut, and deep. 
The specimens have been deposited in the Indian Museum 
and are numbered °93*, 
LITERATURE. 
Wilson, C. B.—North American Parasitic Copepoda of the 
family Argulidae, with a Bibliography of the group and a systema- 
tic review of all known species. Proc. U.S. Nat. Mus., vol. XXV, 
Pp. 635-742, pls. viii-xxvi (no. 1302). Washington, 1902. 
