S cu t u m. Seen externally the basal margin can hardly be separated from the carinal 

 margin, but an internal basal rim shows how far the basal margin extends (PI. I, fig. 13). 

 Occludent margin curved, near the basal angle slightly turned inward. A triangular tooth is 

 placed internally near the basal angle. The occludent margin meets the tergal margin almost 

 without forming an upper angle. Carinal and tergal margïns blend into one another quite 

 oradually. The two valves, of right and left side, are equally convex. Seen externally the 

 surface of the scutum in the larger specimens is not smooth but furnished with a very distinct 

 series of furrows parallel to the carino-tergal margin. 



Tergum (PI. I, fig. 13 and 14). Ouite rudimentary, triangular. The basal angle is not 

 pointed but obliquely truncated. 



Carina (fig. 150 and 15^). Little over half as long as the carinal margin of the scutum, 

 narrow and internally convex. The exterior surface is carinated and has a prominent heel, in front 

 of which the little fork which is imbedded between the capitulum and the peduncle is attached. 



P e d u n c 1 e cylindrical, narrow and extremely short, in the largest specimen covered at 

 the right side for a great part by the overhanging scutum. 



Size. The largest specimen has a capitulum of 7 mm., the whole length being slightly 

 over 7,5 mm. 



Mouth. Labrum (fig. 16 and 16a) bullate, the front part overhanging and triangular. 

 Crest hairy and pectinated, i. e. furnished with a row of smaller and larger, sharp triangular 

 teeth placed close together. Palpi small, triangular, hairs neither very numerous nor very long. 

 Mandibles (fig. 17) with four teeth and a rudimentary inferior angle, produced into a fine 

 point. The teeth are nearly equidistant, tooth 1, 2 and 3 finely pectinated on the inferior side. 

 Mandibles on the front part more densely hairy than in the other species of the genus. 

 Maxillae (fig. 18) with a notch beneath the three upper spines, hairs in the notch delicate; 

 the not very numerous (6 — 8) spines beneath the notch relatively delicate also; covered with 

 dense hairs. Outer maxillae (PI. I, fig. 19) quadrangular, rounded at the corners, hairs not 

 very dense nor very long. 



Cirri, short, very unequal, more or less rudimentary. The cirri of the right side as a 

 rule smaller than those of the left side. The first pair is not far from the second pair. Both 

 cirri of the first pair have unequal rami, but each ramus is composed of 7 segments. The 

 i st cirrus of the right side has the shorter ramus about half as long as the longer, in that of 

 the left side the difference is not so great. Each segment bears a transverse row of strong 

 spines at the extremity and these grow stronger and become more numerous distally. The top 

 of the last segment bears five or six spines. The concave side of each ramus has a group of 

 spines at the extremity of each segment, the convex side is furnished with a row of very 

 delicate hairs. 



The second cirrus of the right side has unequal rami both composed of eight segments ; 

 that of the left side has the posterior longer ramus composed of 10, the anterior ramus of 

 8 segments. The segments are, as in the first cirrus, short, quadrangular or even broader 

 than long. Each segment has a transverse row of spines at the outer side near the extremity, 

 more strongly developed in the terminal segments and towards the dorsal side of each ramus. 



13 



