1910.] J. R. HENDERSON & G. Marruatr: Freshwater Prawns. 281 
included. All measurements are in millimetres, and are taken in 
the case of joints from the dorsal side. The zschium, merus, 
carpus, palm, and fingers of the large chelipedes, are indicated 
respectively by their initial letters i., m., c., p., f.; the abbrevia- 
tions im. f., and m. f., stand for the zmmobile and mobile fingers 
respectively. 
The term young as applied by us includes specimens with the 
chelipedes shorter than the body ; it does not necessarily imply 
that the individuals are sexually immature. 
PALAEMON CARCINUS, Fabricius. 
(Pl. xv, figs. 1a—g.) 
P. carcinus, Fabricius, Suppl. Ent. Syst., p. 402 (1798); Milne- 
Edwards, Hist. Nat. des Crust., t. ii, p. 395 (1837); Ortmann, 
Zool. Jahrb. Syst., Bd. v, p. 700 (1891); de Man, in Max Weber’s 
Zool. Ergebn., p. 421 (1892). 
Characters of adult males.—The rostrum is long, and exceeds 
the antennal squame by nearly one-fifth of its length ; it is bent 
near the middle and upturned distally. The tooth formula is 
Pee 19 (most commonly 2210 39) - the seventh to the eleventh 
10 to 14 Eto. E32 
teeth are usually separated by wider intervals than the others. 
The first three upper teeth, or rarely the first two, are on the 
carapace. 
The large chelipedes are sub-cylindrical and either equal or 
sub-equal; they are nearly half as long again as the body; a 
longitudinal pale line traverses the upper and lower surfaces of 
the palm, carpus, and sometimes the merus. The joints are beset 
with broad-based spines, which are less strongly developed on the 
ischium and the immobile finger, and absent from the mobile 
finger. ‘he distal end of the carpus is about the same width as 
the palm, while the latter is of uniform width. The finger-tips 
are strongly incurved, more especially that of the mobile finger. 
The mobile finger is stouter than the immobile finger, and is 
densely pubescent, a fact which causes it to look stouter than it 
really is. The tooth on the immobile finger is conical, while the 
crenation of the ridge situated proximally to this tooth is well 
pronounced; the proximal tooth of the mobile finger may, in 
some cases, be followed by a small tubercle. When the fingers are 
closed, the tooth on the immobile one lies nearer the proximal 
than the distal tooth of the mobile finger. The following measure- 
ments are taken from the chelipede of an adult specimen (dried) 
measuring 295 mm. in total length :— 
PAs ett os Le. Tilo =p..112. £..89. 
The telson-tip is acutely pointed ; the inner sub-terminal spinule 
on each side projects backwards beyond the outer one, but does not 
nearly reach the tip of the telson itself. 
