BIHANG TILL K, SV. VET. AKAD. HANDLINGAR. BAND. 4- N:0 8. 9 



In the general form of its body Pterygocera differs 

 very much from its allies among the Gammaridae by its greater 

 breadth and more considerable convexity as vv^ell as by the 

 shortness and feeble development of the hinder part of the 

 body. While, namely, in the allied Gammaridae, the hinder 

 part of the body (pleon and urus) constitutes a considerable 

 part of the total length (more than the third, the half, often 

 more than the half), here it answers to scarcely the fourth 

 part of the same. The coxae of all the pereiopoda are large, 

 as are likewise the bases and the next following joints of the 

 three last pereiopoda, forming when jointed a harnesslike 

 shelter for the greater part of the lower side of the body, an 

 arrangement which reminds very much of certain Platyscelidae 

 of the Hyperidean group, f. i. Thyropus, Dithyrus and others. 

 The total length of the animal reaches 10 — 12 millimeters. 

 The colour is almost like that of the sand, wherein it lives, 

 light yellowish grey. 



The cephalon, including the rostrum, is scarcely as long 

 as the two first segments of the pereion. Anteriorly it con- 

 tracts rather snddenly into the short, triangulär, flat and feebly 

 declining rostrum. This is about one fifth of the whole length 

 of the cephalon, and does not reach farther than to the third 

 part of the first joint of the superior antennas. The upper 

 contour of the cephalon is feebly curved, the posterior margin 

 almost straight, the inferior and anterior is semicircular with 

 two prominences, the foremost of which, opposite the inferior 

 antennse, carries the eyes; the posterior, close behind the same 

 antennae, is forming the front-border of the region of the mouth. 



The pereion is considerably more than twice as long as 

 the pleon and far more strongly developed. The first segment 

 is the strongest, from thence the segments increase in length 

 to the fifth, which is the longest; the last two are a little 

 shorter and almost of the same size. 



The coxae on the first four segments are longer than broad, 

 on the last three broader than long. The first two are com- 

 paratively small, pearshaped. The first rounded at the point, 

 bordered with small unciliated hairs. The second a little lon- 

 ger than the former, pointing downwards, the inferior bor- 

 ders, armed with unciliated hairs ; the very point carries 

 a long, strong, close-ciliated bristle. The coxa of the third 

 segment is twice as long as the preceding, formed like a shor- 



