CRUSTACEA COPEPODA. It. 
47 
but is yet distinguished by several features. The antennulee (Pl. III, figs. 7 a and 8 d) are divided into several 
joints, of which the two or three distal ones are well marked off. The antennee have an unjointed exopod of 
very considerably length (figs. 7 a and 8 d) and with terminal setee; this exopod is wanting in Chondracanthus 
(already pointed out by Kroyer). The mandibles have the saw-teeth less numerous and more coarse than in 
Chondracanthus. The maxillulz are, partly or completely (?), seen on fig. 8c and marked mx. The maxillipeds 
(fig. 8e, mp) are more slender than in Chondracanthus and their second joint not produced distally below the 
following joint. Only two pairs of thoracic legs are found in Chondvacanthus — at least in the boreal and arctic 
species —; in Diocus these two pairs are present, but besides the third pair exists at least as a couple of sete, 
the fourth pair is either a minute rudiment or scarcely visible, while fifth pair is proportionately well devel- 
oped (fig. 8c) and may even (in D. gobinus) be distinctly biramous. 
59. Diocus frigidus n. sp. 
(Pl. III, figs. 8 a—8 e.) 
Female. — In general aspect (figs. 8 a—8 b) very different from D. gobinus. The head is produced 
considerably downwards, and the produced part compressed from in front, so that the terminal area with 
antennz and some mouth-parts visible as tiny knots is transverse; antennulee could not be perceived (may 
be lost?) on the single specimen removed from its place. — The anterior part of the trunk is dorsally towards 
the sides (fig. 8 b) and across the ventral surface (fig. 8 a) marked off from the posterior part; on each side 
it is produced into a moderately long and very thick process directed outwards, downwards and backwards. 
The second part of the trunk is much larger, both much longer and broader, than the anterior part; each 
lateral portion is produced backwards into an extremely large protuberance, a little longer than broad and 
tapering with the end rounded; on the anterior portion of the ventral surface of the second part two very 
distant, proportionately somewhat small though rather thick protuberances, about as long as thick, directed 
downwards and somewhat outwards. On the upper side of the same second part two very deep, very oblong, 
very oblique, and rather distant impressions are found a little behind the middle, while the ventral surface 
has two distant, deep and somewhat triangular impressions united by a more feeble transverse impression. 
— The abdomen is a rounded protuberance distinctly broader than long. — The ovisacs in the specimen 
delineated somewhat unequal in length, the longest one being about twice as long as the median line of 
the animal. 
Length in the median line 5.7 mm. 
Male (fig. 8c). So similar to the male of D. gobinus that it is uncertain whether all the rather few 
and on the whole small differences found between them are of specific value. The major proximal part of the 
antennule (fig. 8 d) is not as broad as in D. gobinus (fig. 7 a), but this feature may be uncertain, and besides 
the number of joints can not be ascertained with real certainty in any of the two species. The exopod of the 
antenna (fig. 8 d) a little longer and more slender than in D. gobinus (fig. 7 a), with its terminal part somewhat 
different. Third joint of the maxillipeds (fig. 8 e) shorter and a little thicker than in D. gobinus. The two 
anterior pairs of legs small, but with two minute rami in both species; of third legs in D. frigidus only a couple 
of setee is visible, while in D. gobinus the leg itself is present as a minute knot; fourth legs could not be seen 
