II4 Records of the Indian Museum. [Mor. Vile 
The most conspicuously primitive feature of the genera Xipho- 
caris and Xiphocaridina is the possession of well-formed exopods 
on all the peraeopods, a schizopod-like character which they share 
with one other Atyid genus, Palaemonias, Hay, from the mam- 
moth cave of Kentucky. In three other genera, Syucaris, Troglo- 
cavis and Atyaéphya, exopods are also found on certain thoracic 
legs, but never on all, while they are uniformly absent from Atya, 
Caridina and Ortmannia, genera which comprise the large majority 
of known species of the family, and from Limnocaridina, Caridella 
and Aftyella that constitute the peculiar Atyid fauna of lake Tan- 
ganyika. 
Until comparatively recently the distinctions between Xzpho- 
caris and Xiphocaridina were not recognized ; but Bouvier (1g0Qa) 
had pointed out that the West Indian X. elongata, the type of the 
former genus, differs from its supposed congeners in New Zealand, 
China and Australia in several important structural features. 
He consequently created for the latter species a new genus, 
Xtphocaridina. 
Xiphocaridina is distinguished from Xiphocaris by the pres- 
ence of supra-orbital spines on the carapace, by the anteriorly 
excavate carpus of the first peraeopods, by the presence of tufts 
of hairs on the tips of the fingers of the chelae (a character found 
in all Atyidae with the exception of Xzphocarts) and by the absence 
of arthrobranchs at the base of the first four peraeopods. 
From a consideration of these characters it is evident that 
Xiphocaridina has proceeded on a line of specialization similar to 
that which has resulted in the evolution of Cartdina and this fact 
determined Bouvier in his choice of its name. Xzphocaris, as at 
present understood, is the most primitive genus in the family ; except 
for the complete suppression of the mandibular palp, it bears a 
very close resemblance to the Hoplophoridae. 
Palaemonias, Hay (1902, p. 226), is distinguished from both 
the preceding genera by the distal excavation of the carpus of the 
second pair of peraeopods and by the unpigmented and non-facet- 
ted eyes. It appears to resemble Xiphocaris in the absence of a 
suptra-orbital spine and X7phocaridina in the reduction of its bran- 
chial system.! 
Up to the present time only the following species of Atyidae 
with the full number of exopods on the thoracic limbs have been 
described :— 
Xiphocaris elongata (Guerin). 
Cuba; Hayti; Dominica; St. Domingo. 
Xiphocaridina compressa (De Haan). 
Yokohama; Tokio ; Flores ; Queensland ; Victoria ; 
New South Wales; Norfolk Is. 
1 Hay states (p. 229) that ‘* the gills seem to be only four in number, on each 
side attached to the first four peraeopods, but there may bea rudiment on the 
fifth.’ In Xiphocxvidina there are seven gills (one rudimentary) on either side 
and twelve (one rudimentary) in X7phocarts. 
