BORRADAILE— ON THE PONTONIIN^ 337 



but tends to become simple. In this respect it is very variable, and tbe maxillse 

 of the two sides may differ in the same individual. The lobe is simple in the species of 

 Pontonia and Conchodytes (Plate 57, fig. 26/") I have been able to examine*, and also in 

 the only specimen oi PericlimencBus rohustus I have dissected (Plate 55, fig. 20/), in some 

 Coralliocai'is (as C.japonicus, Plate 56, fig. 23/) though not in others (as C. macrophthalma, 

 Plate 56, fig. 24), and, according to SoUaud, in Harpilius. In Harpiliopsis it is double, 

 with obsolescent proximal lobule. From the frequent occurrence of reduction in the lobes 

 of this limb in the Carides, it would seem that they are not of great physiological 

 importance. The endopodite is gently swollen at the base, perhaps by the remains of the 

 fifth endite, and the exopodite (scaphognathite) varies in shape and width with the gill- 

 chamber, being broad in depressed forms, particularly in Harpiliopsis and Coralliocai'is. 



In the Jlrst maxilliped [g in figs.) two endites — the second and third — are nearly 

 always recognizable, and usually separated by a very distinct notch. The edge of 

 the proximal (second) endite is often indented by a shallower notch. The endopodite 

 is usually simple and tapering, with a stout bristle at a short distance from the 

 tip, which may perhaps represent a joint. In the Anchistus-Conchodi/tes group the 

 endopodite is shorter and blunter, and often shows traces of a transverse joint. At 

 the tip of the exopodite (exognathite) a few small joints may or may not be present, 

 and at its base on the outer side is a fringed lobe (the lobe a of Boas) which generally 

 varies in width with the body of the species, though it is wider than this would indi- 

 cate in Urocaridella (Plate 53, fig. 2 g) and some Urocaris. The epipodite (mastigobranch) 

 varies greatly in size. Its outer border is usually notched, but in Periclimenes the 

 notch is shallow or wanting. It is deep in Uroccmdella, which is remarkable if it is to 

 be regarded as an unprimitive feature. The lobes separated by the notch may be equal, 

 or the distal one may be longer than the other and pointed. 



The second maxilliped (h in figs.) has the typical caridean form, that is to say, 

 (l) its main axis consists of six joints, owing to the fusion of the basipodite and 

 ischiopodite, (2) the last two joints are bent strongly backwards, so as to lie parallel 

 with the ischiobasipodite, (3) owing to the growth backward (morphologically forward) 

 of a process of the propodite on the outer (morphologically inner) side of the dactylo- 

 podite, the latter comes to lie not at the apex of, but along the median side of the 

 propodite. Thus these two joints are compacted into a firm plate, which presents 

 a long median margin, fringed with bristles, against its fellow of the opposite side. 

 To the third of these characters there is an exception in the case of the genus 

 Harpilius, where, according to Dana's figure for the type species {H lutescens), there 

 is a very remarkable return to the primitive condition in respect of the position, 

 though not of the shape, of the dactylopodite. This arrangement is approached in 

 at least one species of Coralliocaris {C. superbus). The exopodite is obscurely annulate 

 in the greater part of its length, and bears at the end a comparatively small number 

 of true joints. The coxopodite carries on the outer side a simple oblong epipodite, 

 and on the median side a knob bearing bristles which probably represents an endite. 



* Pontonia ascidicola and Conchodytes meleagrince and tridacnoB. Ortmann (Zool. Jahrb. Syst. v. 

 PL 37, figs. 9 f., 10 f.) figures a cleft in the maxilla of P. tyrrhena. 



SECOND SERIES— ZOOLOGY, VOL. XVIL 43 



