10 c. BOVALLIUS, NOTES ON PTERYGOCERA ARENARIA, SLABBER. 



tened crescent and provided "with short hairs at tlie top. That 

 of the fourth segment is as long as the preceding one, but 

 broader, "with some few small bristles on the posterior börder. 

 The coxa of the fifth segment is the largest of all, shorter 

 than the preceding one, but more than twice as broad, feebly 

 haired. That of the sixth is considerably smaller, but more 

 strongly haired. The coxa of the seventh segment is the 

 smallest, scarcely the half of the preceding one. 



Tlie pleon has the first two segments of about the same 

 size and little developed, the third being equal in length to the 

 two preceding taken together, cylindrical, rounded in the po- 

 sterior end, hollow on the lower side, so as to cover the urus 

 and its appendices. 



The urus is very short, shorter than the last segment of 

 the pleon, to which it is articulated, not in the ordinary way, 

 but fastened to its lower side just within the posterior margin. 

 In consequence it can fold itself under this segment and is 

 then totally concealed. 



All the segments of pereion and pleon are plain and 

 without spines or bristles, excepting, as said already, on the 

 coxae. On the contrary the last two segments of the urus 

 carry on their back-side some straight simple spines (Pl. II, 

 fig. 17). 



The eyes are placed on the foremost lobe of the anterior 

 side of the cephalon, a little above the bases of the inferior 

 antennjB. The layer of chitine covering the eye is but little 

 thinner than the rest of the covering of the cephalon, on the 

 lower side feebly hoUowed to a kind of orbit, in order to give 

 room for the eye-globe, which is not completely globular, but 

 rather cubiform with rounded angles. In the adults the dia- 

 meter of the eye-globe is 0,2 5 millimeter, in the young spe- 

 cimens somewhat larger, and its form more globular; with 

 the age of the animal the size of the eyes diminishes also, and 

 in the oldest they are discovered only with difficulty. The 

 pigment is red, the eye-lens short, thick, bluntly conical, the 

 surface of the eye irregularly facetted. 



The superior antenncB are inserted under the front-surface 

 of the cephalon, each on its side of the rostrum, which covers 

 a part of the first joint of their peduncles; they are about twice 

 as long as the cephalon with the rostrum. They are as usual 

 composed of a three-jointed peduncle, a flagellum and a se- 



