69 
described anywhere in the literature, viz. the carina in the sixth 
abdominal segment. This carina goes in the specimens, that from 
the antennal plate and the second pereiopod are to be ascribed to P. 
tarda, just to the hind edge of the segment (fig. 1), but is in the hinder 
part divided into two almost parallel carines; in P. princeps the 
hinder part of the segment is simply compressed without any 
carina (fig. 1). 
That the proportion in the length of antennal plate, carapace 
and abdomen cannot be used, appears from the following measurements ; 
the specimens are determined from the shape of antennal plate, cara- 
pace and sixth abdominal segment) (the measurement are in mm.) 
P. tarda 
| | 
É i Abd 
Locality Total ein i me Carapace | rerk Aalen 
Skagerak Eg get 12 25 46 
70 , 10 21 40 
me 79 12 24 44 
Su 68 95 20” 4 80 
re: 11401 14 SE ul 
629 49' N, 189 46' W. 75 11 B8 | 42 
P. princeps. 
| | Abdomen 
fan Total length | for ren Carapace | excel. Såldon 
mn >= mm minen == | 
S. Greenland (Kriger s | 
ype—specimen of | 
ARE ng 108 imperfeet | — 38 se 
672 19'N, 159 52" W. 605" 5 38 
659 28' N, 279 297 W. VG 0 RR KR ø 
Even the form of the antennal plate may cause some diffi- 
culty. Thus I have seen one, otherwise somewhat typical P. tarda 
from the Skagerak, whose right antennal plate is as in P. princeps, 
whilst the left has the same form as in P. tarda (Kemp 1. c.…. 
1908 (1910), pl. 4, fig. 9); but from the measurements (antennal 
plate 10,5, carapace 23, abdomen excl. telson 38) it might be 
determined as P. princeps. 
