244 Records of the Indian Museum. [Vor Vile 
crabs of the genus Potamon (especially P. mami, Rathbun) in 
hill-streams in parts of Tenasserim. 
The Temnocephaloidea appear to be confined to fresh water 
and to live, without exception, symbiotic rather than parasitic 
lives. In habits they are predaceous, but they invariably attach 
themselves to a host which they can conveniently employ as a 
beast of burden and a stalking-horse in the pursuit of their prey. 
Each species affects a single host or a group of closely allied 
hosts. Most of the Temnocephaloidea are found attached to 
Decapod Crustacea; the Australian species inhabit the gill- 
chamber of crayfish; the Malayo-Burman Temmnocephala sempert 
lives on the ventral surface of crabs; one S. American form 
attaches itself to equatic tortoises, while another penetrates within 
the pulmonary chamber of the Gastropod Ampullaria. The 
species to be discussed in this paper, like the allied European 
form, is associated with small prawns of the family Atyidae. 
The Temnocephaloidea may conveniently be divided into three 
families as follows :— 
I. At least four anterior tentacles; posterior sucker circular ; 
alimentary canal much shorter than body, with the 
genital organs posterior to it. 
A. No lateral tentacles; no anterior 
sucker; pulsatile excretory 
pouches present .. .. TEMNOCEPHALIDAE. 
B. Lateral as well as anterior ten- 
tacles; an anterior sucker in 
front of the mouth ; no pulsatile 
excretory pouches. . .. ACTINODACTYLELLIDAE. 
II. Only two anterior tentacles: ante- 
rior margin of posterior sucker 
cleft; alimentary canal extend- 
ing to posterior extremity, with 
the genital organs on its ven- 
tral surface; no pulsatile ex- 
cretory pouches .. .. SCUTARIELLIDAE. 
The third family appears to be considerably more remote 
from the two first than either of the latter is from the other, 
but it has not hitherto been recognized as distinct. It consists 
of two allied genera, Scutarielia, Mrazek, and Caridinicola, gen. 
nov. ‘The former is known froma single species from Montenegro ; 
the latter from a single Indian species. The family may therefore 
be said to agree with most of the secondary divisions in the 
Temnocephaloidea in consisting almost of a minimum of forms. 
Only 5 genera (Temnocephala, Craspedella, Actinodactylella, Scu- 
tariella and Caradinicola) are known in the ‘‘ Class’’ and of these 
Temnocephala is the only genus that is not monotypic, while the 
Temnocephalidae is the only family hitherto recognized that 
includes more than one genus, Craspedella as well as Temnocephala 
belonging to it. 
