BORRADAILE— ON THE PONTON IIN^ 341 



several cases (^Periclimenes spiniferus (Plate 52, fig. Ih), P. soror, etc.) they have a comb- 

 like arrangement of fine teeth on the opposed edges of their fingers, and in others the 

 tips of the fingers are double. The chela usually bears tufts of stiff hairs. The first 

 three joints may show traces of the bristle-bearing ridges found in species of Leander. 



The legs of the second pair are the stoutest limbs of the body, and nearly always 

 longer than the first pair. They may be equal or unequal, alike or unlike, and that 

 sometimes within the limits of one genus. They are rarely of complicated shape. 

 Their fingers have usually some stout teeth on the apposed edges, but sometimes 

 they are blade-like. In Periclimenes denticulatus they are edged with numerous fine 

 denticles. In P. petitthouarsi and P. spiniferus (Plate 52, fig. 1 1) each finger of the larger 

 member of the pair bears a curious pit with raised edges, and in the great chela of 

 PericlimenoBus (Plate 55, figs. 19, 20) a knob on one finger fits into a socket on the other, 

 somewhat as in Alpheus. Curiously enough, in one of the two species as yet discovered 

 the knob is on the fixed finger, while in the other it is on the " thumb " or movable 

 finger (dactylopodite) as in Alpheus. 



The stoutness of the limb varies, roughly speaking, with that of the body. In 

 Urocaridella (Plate 53, fig. 2 a) and Urocaris it is very slender throughout. In Palmmo- 

 nella (Plate 53, fig. 5 a) it is stouter but still slender. In Periclimenes it varies in stoutness 

 but is never very heavy. In Ancyclocaris it is short and rather stout. In Periclimenceus 

 one is massive and Alpheus-like in keeping with the general build of the body, and the 

 other smaller and simpler but somewhat of the same type. In Harpilius lutescens both 

 are rather slender and insignificant. In Pontoniopsis the larger is heavy, but not 

 monstrous, and of fairly simple shape, while the smaller is very slender. In Harpiliopsis 

 the palm is long and fairly heavy, and in Coralliocaris (Plate 56, figs. 23 I, I') this tendency 

 is enhanced and the chela is a characteristic organ, long and heavy, swollen at the 

 base, and narrowing towards the fingers, which are short. In Anchistus it is of moderate 

 size, with parallel sides and fingers of a good length. In Pontonia (Plate 57, fig. 29) and 

 Conchodytes it grows heavier, but the palm is still generally of fairly even width and 

 the fingers generally not very short, though in some cases there is an approach to the 

 condition of Coralliocaris. The same may be said of Typton. 



The thumb is on the outer side of the limb, and usually moves in a nearly horizontal 

 plane, but a little upwards or downwards*. Sometimes, however, it becomes almost 

 or quite vertical, and in this case it is generally above the other finger, but may be 

 below, as in Coralliocaris japonica (Plate 56, fig. 23 /). 



In many cases, especially in Periclimenes (Plate 52, fig. 1 a), one or more stout spines 

 are found at the end of the "wrist" (carpopodite), or "arm" (meropodite), or both. 



The mode of use of the chelipeds is as yet unknown. Presumably those of the 

 first pair serve as cleaning organs, as they certainly do in Leander. They are no doubt 

 also used to convey food to the mouth, as in Leander. The chelse of the larger pair 

 are perhaps, as in other cases, used for seizing and tearing masses of food and as weapons 

 of offence both against prey and against foes ; but they seem unsuited for handling 



* This fact is exaggerated in many of the figures, by slightly twisting the hand, in order to show the 

 shape of the fingers. 



