I. '08. 44 



The carapace in all the specimens is dorsally carinate 

 throughout its length, and the abdominal sonntes, with the 

 exception of the posterior portion of the sixth, show a similar 

 character. The usual lateral carinae are present on the sixth 

 somite and on the carapace above the branchial region. The 

 antero-lateral sinus is almost rectangular in the large speci- 

 mens ; in small individuals it is slightly obtuse. 



The antenna! scale is about four times as long as wide and, 

 as mentioned above, its outer margin is strongly convex dis- 

 tally and terminates in a very short tooth. 



The merus of the first pair of pereiopods bears from 4 to 8 

 spines on its ventral margin ; the inferior distal angle of the 

 basus is produced to a rather blunt point , and neither it nor the 

 ischium are furnished with spines. The merus of the second 

 pair is provided with 12 to 18 ventral spines ; the ischium in 

 some specimens shows a single spine on its basal edge, in the 

 others it is unarmed. The basus is in some specimens un- 

 armed, in the others it bears from 2 to 4 spines. Fig. 7 show^s 

 the greatest development of these spines found. 



These spines on the basal and ischial joints have not been 

 noticed before, and they are very possibly absent in West 

 Atlantic and Pacific examples. The spinulation of the merus 

 is, however, known to be very variable (cf. Faxon, 1895, and 

 Eathbun, 1904) ; in some specimens the merus of the first pair 

 is reported to be unarmed, while that of the second pair is 

 provided with only six spines. 



The Irish specimens differ from the original description in 

 having the telson shorter than the inner uropod ; the authors 

 mentioned above have not made any reference to this character 

 when dealing with other specimens of the species, but, judg- 

 ing from the great variation shown in certain other Caridea, 

 is not of any special importance from a systematic point of 

 view. 



I am of the opinion that some at least of the specimens re- 

 corded by Wollebaek (1909) as Pasiphae tarda should be re- 

 ferred to this species. His figure (pi. xiii) of one of the 

 '' gigantic specimens, 140 to 160 mm. long," from the S. coast 

 of Norway, is evidently drawn from a specimen of P. princeps. 



Size. — The largest specimen observed is a male measuring 

 132 mm. ; the type specimen is a female, and measured 215 

 mm. (Smith). 



Colour. — The carapace and abdomen are of a uniform bright 

 vermilion red ; the pereiopods are the same colour, with the 

 exception of the fingers of the chelae, which are much darker, 

 almost maroon in fact. The eyes are leaden black. The an- 

 tennal scale is milk white, with a narrow red stripe externally 

 and a broader stripe along its inner margin ; the basal segment 

 is also milk white, outlined with the same red tint. The 

 antenna is white, w4th a red dorsal stripe ; the antennules and 

 all the other appendages partake of the prevailing vermilion 

 red colouring. 



