CRUSTACKA MA1.ACO8TRACA. III. 



also mentioned the strong teeth on the body of C. stygia as a generic character, but as two completely 

 blind new species described later on have the body more smooth than some of the species of Gnalhia, 

 and as these new forms do not afford any other generic difference from Gnathia, the armature with teeth 

 or processes in C. stygia cannot be included in the generic diagnosis for Cafcognalhia. And to establish 

 a genus of such animals as Gnathia only on the absence of eyes would be about as incorrect as sepa- 

 rating the blind species of Afitttna from this genus. 



New species of Gnathia ought to be established on the males; in the females of different spe- 

 cies it is not (infrequently difficult to point out reliable specific characters, and at the present state of 

 our knowledge many of the larvae cannot be referred to species with real certainty. The males of 

 several species show considerable individual variation, especially as to size and degree of scabrosily, 

 which renders the description and determination far from easy. One of the most important characters, 

 vit, the shape of the frontal margin of the head, is frequently difficult to make out, and the proximal 

 half of the upper margin of the mandibles ought always to be inspected from the side. 



The material comprises male specimens of seven species, two of them new ; the following key 

 may be a help for the determination. It may be mentioned here that neither G. maxillaris MonL nor 

 G. oxyuraa Lilljeborg ' are known from our area, though I suppose that the last-named form may live 

 at the Fa-roes. 



A. Eyes well developed. 



a. Proximal half of the upper margin of the mandibles only with a protruding angle at the cud. 

 Dorsal surface of the thorax and especially of its posterior segments with conspicuous irregular 

 depressions . ,. G. elongata Kr. 



b. Proximal half of the upper margin of the mandibles with some irregular teeth. Thoracic surface 

 not areolated from depressed areas. 



. Front margin of the head at the middle with a small protuberance, or feebly concave. 



. Head and thoracic segments with very few and short seta?. Major distal part of the last 



abdominal segment is shaped as a narrow triangle a. G. robitsta (!. O. S. 



. Head and at least the three anterior free thoracic segments with a good number of long 

 setae. Major distal part of the last abdominal segment is shaped as a moderately broad 



triangle 3. G. hirsute G. <X & 



/?. Front margin of the head at the middle with a deep and moderately broad incision. (Major 

 distal part of last abdominal segment is shaped as a narrow triangle). 4. G.abyssorum G. O. S. 



R No eyes. 



a. Tergite of the penultimate leg-bearing thoracic segment not divided in the median line. Side* 

 of the thoracic segments without processes or teeth, at most some of them with a few granules. 

 Small forms. 



i In the list of the Danish species of mot orden of Malacustraca <Vi<l Mold. Naturh. Forming Kjflbenbara for 1909) 

 I have made an error which may he corrected here. I referred the Danish specimen* of titaikia to IS. uHuaHaru Moat. M 

 figured and described by G. O. San (Account, II, p. 51; PL ai; Ft it. fig. n which to correct, but I overlooked that Norman 

 in 1906 had pointed out that G.majfiUarit Mont ia another species, and that the specie* described by Sara, cooseqacatly 

 also the Danish specimens, most be named G. oxr*rra Litljeborg. A few months ago I looked over the entire material from 

 Denmark and found that all specimens belong to the last-named species. 



