244 Transactions. — Zoology. 



end. The whole limb is densely spined : the basos has one 

 spine on the inner margin ; tlie ischios has a few on the inner 

 margin, and one or two indistinctly marked on the outer mar- 

 gin ; the meros has two irregular rows on the inner margin, 

 and one row on the outer margin, and one spine on each side 

 of the hinge ; the carpus is spined all round, with a slight 

 groove above, between two longitudinal rows ; the propodos is 

 densely spined in longitudinal rows, the largest spines being 

 on the upper surface and the inner margin, and in one row of 

 about six on the lower surface ; there are two very regular 

 rows on the outer margin, extending right to the end of the 

 fixed finger. Both fingers are very spinous, inner margins 

 with rounded teeth and a few hairs, the fingers ending in 

 incurving spines. The pleura of the abdominal segments have 

 the infero-posterior corner distinctly angled, the anterior edge 

 being longer and more convex than the posterior, which, 

 though slightly sinuous, scarcely curves forward ; the anterior 

 edge alone fringed with setae. 



The specimen I have described is the largest of P. lilani- 

 J'rons that I have seen. I have two others from Nelson, 

 4-8in. long, and others from Lake Eoto-iti, 4-15in. and 4in. 

 long. On the other hand we may have mature specimens 

 very much smaller : thus I have a female bearing eggs, 

 from the Thames, only 2-4in. long, and another, from Wel- 

 lington, 2 -Sin. From the measurements given in the table 

 below it will be seen that the proportion of the greatest breadth 

 of the carapace to the length varies to some extent, but is 

 almost always less than one-fourth the length. When seen 

 in dorsal view the sides of the branchiostegites are nearly 

 parallel, so that the carapace is about the same width through- 

 out the whole length of the branchiostegites. The sides, how- 

 ever, sometimes bulge slightly in the centre, but not to so 

 great an extent as the Avon and Heathcote specimens of 

 P. neo-zclanicus. (See Plate X., fig. 1, and compare it with 

 fig. la.) The number of teeth on the rostrum varies 

 very greatly, and very often difi"ers on the two sides ; the 

 median teeth below are sometimes entirely absent, as in the 

 Pelorus Eiver specimens, where they are present in one speci- 

 men only. The spines, too, vary in distinctness, being very 

 sharp and distinct in the Nelson and Greymouth specimens, 

 but blunt and more or less rounded at the end in those from 

 Lake Eoto-iti. The rostrum is frequently depressed, as in the 

 Napier specimen, but, again, is often quite horizontal, or only 

 very slightly depressed. The median ridge on the carapace, 

 behind the rostrum, varies much in length and distinctness, but 

 usually does not extend so far back as in P. nco-zelanicus. With 

 regard to the spines on the carapace, it must be remembered 

 that the groups into which I have divided them, though useful 



