On a new Species o/Arcturus. 291 



XXXVIII. — On a new Species o/'Arcturus(A. damnoiiiensis). 

 Bj the Rev. Thomas R. R. Stebbing, M.A. 



[Plate XV.] 



Arcturus damnoniensis lias three conical tubercles on the 

 head — one medio-frontal, with the other two side bj side behind 

 it. Each of the body-segments has a similar elevation — that on 

 the elongated fourth segment, not quite so far back as the centi-e 

 of its dorsal surface, being the most considerable and conspic- 

 uous. To this almost central tubercle the dorsal surface of the 

 segment slopes rather steeply up and then rather steeply down to 

 a second tubercle, truncated at the top and standing over the 

 posterior margin. The tubercles of the other segments are 

 less important in size and more sharply pointed than those of 

 the head and the fourth body-segment, that on the second 

 segment being the most diminutive. 



Of the pleon or tail three segments are clearly defined : — the 

 first very short ; the second less so, and dorsally raised above 

 both the first and the last, the long terminal piece having also 

 a small dorsal elevation in close proximity to that of the 

 second segment. The terminal piece has also at the base a 

 lobe on each side running out into a sharp angle. Further 

 back the lateral margin is again produced into a similar angle j 

 between this and the rather obtuse apex there is a slight in- 

 dentation in the margin on either side, the two being connected 

 by a small dorsal furrow. 



The upper antennae are about as long as the head ; they 

 have a large basal joint, followed by three slender almost trans- 

 parent articulations and a short seta, the last articulation being 

 longer than the two which precede it both together. 



The lower antennae are as long as the body ; four joints are 

 visible and a stiff little-divided flagellum. The first of the 

 four joints is short and thick with a deep external notch ; the 

 second is long, clubbed at the distal end ; the third is longer 

 again ; the fourth is about the same length as the second, but 

 slender and uniform in thickness. All the joints have short 

 outstanding hairs or bristles. The third joint is longer in the 

 male than the female, and in each about corresponds in length 

 with the fourth body-segment. 



The female is altogether more strongly tuberculated than 

 the male ; and the lateral dilatations over the insertions of the 

 legs are also more pronounced in the female than in the male. 

 The most striking difference, however, between the two sexes 

 is in the fourth body-segment ; for this segment in the female, 

 besides carrying the brood-pouch, is dilated at its origin into 

 a large triangular lobe on cither side, while in the male there 



