1g10.] J. R. HENDERSON & G. Matruar: Freshwater Prawns. 287 
as the latter. The following are the measurements of a young 
specimen measuring 72 mm. :— 
ris m. (oe p. ih 
Rechelipede =...) £35 14°5 26 15 1G 
i chelipede~ =< ~ 13°5 14 24 14°5 10'5 
General vemarks.—On comparing this species with Heller’s 
description and figures, we find that it agrees in a great many 
respects with P.id@. ‘The large chelipedes have the same general 
build, and the joints show almost the same relative lengths. The 
following differences, however, appear to exist :—Heller states 
that the inner margins of the fingers are toothless, and that the 
2 hOsCO ET : eS : 
tooth-formula is Patol ae while his figure shows the large cheli- 
5 
pede to be stouter. Hilgendorf’s figures based on specimens from 
Zanzibar which he refers to P. id@, seem to agree with those of 
) 
Heller except that the tooth-formula is 3 and the chelipedes 
are even stouter than in Heller’s figure. 
Von. Martens thinks it probable that P. sundaicus, Heller, 
from Java, in which the carpus is shorter than the propodus, is 
the young of P.zd@. Ortmann rejects von Martens’ view on the 
assumption that the carpus, which, in the young, is already 
shorter than the propodus, can never, as a result of growth, exceed 
it in length; while this observation is true of most species of 
Palaemon, we have reason to believe that it does not apply to the 
present one. From observations carried out on a large number of 
specimens, we are able to state that the fingers in the present 
species elongate less rapidly with advancing age than do the merus 
and carpus, and the palm does not grow so quickly as it does in 
P. carcinus and P. malcolmsonii, with the result that in adult 
males the carpus is longer than the propodus. Our observations, 
therefore, seem to corroborate von Martens’ supposition. More- 
over young male individuals and females of the Indian species 
which we refer to P. ide, agree closely with Heller’s description 
and figures ; his specimen, which was probably a female, measured 
3 inches in length. 
While Heller’s account of P. sundaicus appears in his paper 
before that of P.zd@, the latter name is preferable, because the 
description is based on the characters of an adult male, while 
some uncertainty must attend the identification of the former 
based as the species is on a female specimen. 
Nobili has referred to P. sundaicus a single specimen from 
Pondicherry, which measured 55 mm. in total length, with the 
3g! 
rostral formula —. 
P. lancetfrons, Dana, originally recorded from Manila, in 
which the carpus nearly equals the palm in length, is perhaps also 
the young of P. id@, but in a slightly more advanced stage than 
