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 
pait divided into two almost parallel carines; in P. princeps the 
hinder part of the segment is simply compressed without any 
carina (fig. 1). 
r 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 
Locality 
Total length 
Antennal 
plate 
Carapace 
Abdomen 
excl. telson 
Skagerak 
83 
12 
25 
46 
— 
70 
10 
21 
40 
— 
79 
12 
24 
44 
— 
68 
9,5 
20 
30 
— 
101 
14 
33 
65 
62° 49’ N, 18° 46' W. 
78 
11 
23 
42 
P. princeps. 
Locality 
Total length 
Antennal 
plate 
Carapace 
Abdomen 
excl. telson 
S. Greenland (Kroyer’s 
type—specimen of 
P. tardal) 
108 
imperfect 
38 
58 
67° 19'N, 15° 52'W. 
60 
10 
19 
33 
65°28'N, 27° 29' W. 
90 
13 
25 
48 
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), pi. 4, fig. 9); but from the measurements (antennal 
plate 10,5, carapace 28, abdomen excl. telson 38) it might be 
determined as P. princeps. 
