85 



behind these one or two median unpaired spines. In some 

 cases, however, as many as five median spines are present. 

 (See also Hansen, 1908, PL III., figs. 2a-2d.) 



The linea anomurica is distinct, and the sub-marginal part 

 of the carapace is covered with low oblique ridges. 



The carapace, excluding the rosti*um, is as long as the 

 straightened abdomen without the telson. 



The first abdominal segment is partly hidden by the carapace 

 and is very narrow. The second, third, and fourth segments 

 have each a transverse furrow on the tergum. The second and 

 third terga each bear a median spine which points forwards.. 

 Sometimes a spine is present on the fourth tergum also ; it 

 occurs in only one of the Helga specimens. 



The pleura are well developed, and are long and narrow, 

 with blunt ends, except those of the second segment which are 

 broad and rounded. On the first segment they are rudimentary. 

 On the anterior margin they are all fringed with setae, and on 

 the sixth segment on both margins. The telson di:Hers some- 

 what in structure from that of M. tridentata. The basal plate 

 comes to a truncate end and is followed by three small plates 

 in the middle, the central one of which is prolonged in a narrow 

 process extending to the posterior margin. 



The eyes are large but quite devoid of pigment. They var}^ 

 somewhat in shape ; in some the cornea is more or less pointed 

 in front, and in others is quite globular. 



The antennules resemble those of M. tridentata, except with 

 regard to the basal joint of the peduncle, which bears three 

 long spines instead of two. One of the spines, immediately 

 at the base of the second joint, is divided into three points, 

 and bears also two or three small teeth between the larger ones. 

 The antennal peduncle differs from that of M. tridentata in 

 having the spines of the basal joint represented by blunt tubercles. 

 The flagella are as long as the body excluding the telson. 



The third maxillipedes are similar to those of M. tridentata^ 

 except that the two teeth on the internal margin of the merus 

 are shorter, and the terminal teeth on the ischium are more 

 rounded. 



The chelipeds are long and slender. One is usually slightly 

 larger than the other ; this may be either the right or the left. 

 They are covered throughout with small scales, some of which 

 are fringed with extremely short setae, but they are devoid 

 of long hairs, such as are present in M. tridentata. The first 

 three joints are slenderer than the others, the thickening be- 

 ginning at the base of the merus, which is more or less quad- 

 rangular in section. Each of the four edges of the merus ends 

 in a sharp dis al spine. The carpus terminates in two double 

 spines above, and a broader spine below, which has also some- 

 times a double point. The propodite is broadest at the base 

 o: the fingers, which are in contact throughout their whole 

 length. The cutting edges are serrate. The palm is longer than 

 the fingers. 



