CRUvSTACEA MALACOSTRACA. III. 



223 



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 Giiuthm, 

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

 or processes in ('.stygia cannot be included in the generic diagnosis for Caecognathia. 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 Munna from this genus. 



New species of Gnathia ought to be established 011 the males; in the females of different spe- 

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

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

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

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

 viz., 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 Mont, nor 

 G.oxyuraa Lilljeborg 1 are known from our area, though I suppose that the last-named form may live 

 at the Fseroes. 



A. Eyes well developed. 



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

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

 depressions 1. G. elongata Kr. 



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

 not areolated from depressed areas. 



a. 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 2. G. robusta G. O. S. 



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

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



triangle 3. G. hirsuta G. O. S. 



/}. 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. 



B. No eyes. 



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

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

 Small forms. 



' In the list of the Danish species of most orders of Malacostraca (Vid. Medd. Naturh. Forening Kjobenhavn for 1909) 

 I have made an error which may be corrected here. I referred the Danish specimens of Gnathia to G. maxillaris Mont, as 

 figured and described by G. O. Sars (Account, 11, p. 52; PI. 21; PI. 22, fig. 1) which is correct, but I overlooked that Norman 

 in 1906 had pointed out that G. maxillaris Mont, is another species, and that the species described by Sars, consequently 

 also the Danish specimens, must be named G. oxyuraa Lilljeborg. A few months ago I looked over the entire material from 

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



