SCHIZOPODA. 31 



Pleopods in the male agreeing in all points with those of males of the genus 

 Avihlyops. 



Telson (Fig. 16) not quite as long as the last segment of the pleon, triangular in 

 shape, tapering evenly to a narrowly rounded apex, nearly twice as long as broad at 

 its base ; distal half of each lateral margin armed with nineteen spines, increasing in 

 length towards the apex, the terminal ones about one-tenth of the total length of the 

 telson ; median setae absent. 



Uropods broken on both sides, but the inner one possesses a single strong spine 

 on. the ventral surface at the inner posterior angle of the otoeyst. 



Length of the single specimen, an ap,parently adult male, 13 mm. 



There can be little doubt, I think, that Dactylerythrops arcuata, lUig (1906), is 

 the same species as the present one. Minor differences, it is true, are to be noticed. 

 For instance, the visual elements of the eye in lUig's species are represented as larger 

 and less numerous than in D. hodgsoni. It may be that in the former preservation has 

 caused the visual elements to mass in groups of more or fewer lenses, since in the 

 'Discovery' specimen, as the figure (Fig. 9) shows, the visual elements are not 

 regularly arranged, but more numerous in some places than others, an effect probably 

 due to the mode of preservation. 



Moreover, in D. arcuata, the telson is not quite so long compared with the 

 breadth at its base as in D. hodgsoni, and is furnished with only eighteen spines on 

 each lateral margin. But these differences are insignificant when compared with the 

 general agreement between the two species in most points. One or two characters - 

 may be added to the above diagnosis from Illig's description and figures. 



Antennular peduncle long and rather stout, last joint the largest and nearly equal 

 to the combined length of the other two. 



Antennal scale slightly over-reaching the antennular peduncle, about four times 

 as long as broad, outer margin entire, and terminating in a short spine beyond which 

 the apex of the scale is only slightly produced. 



Four species of this genus are now known, D. sarsi (Ohlin, 1901), D. thaumatops 

 and D. goniops, Tattersall (1907), and the present species. 



From the other three species, D. hodgsoni is at once distinguished by the shape 

 of the eye. In D. sarsi the eye js acutely pointed in front ; in D. thaumatops it 

 is of quite peculiar form, with an outer equatorial membranous ridge, while in 

 D. goniops the eye is quadrangular, rather than pyriform in shape. Otherwise the 

 four species are rather closely allied and form quite a distinct generic group to 

 themselves. 



D. hodgsoni is at present only known from very deep water in the Antarctic 

 Ocean. Illig's specimens were collected over a depth of 4000-5000 metres, while the 

 present specimen was dredged in 2030 fathoms {ca. 3700 metres). 



H 2 



