§9 



The upper Iatus is trapeziform. There is a short but distinct carinal margin, the 

 leneth of which is about one fourth that of the scutal margin. The scutal and basal margins 



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meet together at a rather sharp angle. 



The rostral latus quadrangular. Basal and scutal margins nearly parallel to each 

 other, the second twice as long as the first. Rostral margin nearly straight and only a trifle 

 shorter than the slightly convex lateral margin. 



The i n f r a - m e d i a n latus is triangular, with a well-developed basal margin and the 

 umbo at the apex. lts rostral margin is slightly hollowed out, its carinal margin slightly convex. 



The carinal latus is very large and has an irregular pentagonal shape. lts carinal 

 margin is divided into two : a large part meeting that of the same valve of the other side 

 along the whole length and a very short part separating the valve from the carina. The latter 

 margin forms an angle with the upper margin and here the umbo of the valve is situated. 

 Upper and lateral margins of about the same length ; basal margin very short. 



The peduncle is short and has a conical shape. The surface is covered with rather 

 large scales, which are chitinous but not very prominent. They are placed in seven not very 

 distinct longitudinal rows. 



Si ze. The specimen figured PI. VII, fig. 16 has a total length of 5,2 mm., the length 

 of the capitulum being 4 mm. They were found attached to a small stem of what I take to 

 be a calcareous coralline. 



The study of the structure of the animal within the capitulum has yielded the fol- 

 lowing results : 



Mout h seen from above triangular, with the part directed forward rounded and bullate. 

 Labrum with a row of small but distinct teeth ; p a 1 p i conical with a tuft of spines at the 

 tip and a row of half a dozen shorter spines or hairs along the outer margin. 



M a n d i b 1 e s with three teeth ; the distance between the extremities of tooth 1 and 2 

 twice as great as that between tooth 2 and 3. Inferior angle pectinated and at a very short 

 distance from tooth 3. The upper margin of tooth 3 shows traces of being pectinated - 

 showing agreement with Sc. balanoides Hoek also in this regard. 



Maxillae with the outer edge deeply notched about the middle; above the notch 4 

 spines, two of which are longer; beneath the notch the edge bears 5 or 6 spines and is 

 slightly protuberant. 



Second maxillae not larger than usual and of the ordinary shape ; spines in three 

 oroups, with some distance between two-, openings giving entrance to the body-cavity at the 

 tip of a swelling — not at the end of a tubular process. 



Cirri. First pair close to the mouth and at some distance from the second pair. 

 Rami unequal : shorter ramus slightly broader, composed of 5 or 6 segments ; longer ramus 

 more elongated, having 7 segments. In both rami the limits of the segments are indistinct ; 

 they bear numerous hairs, partly at the surface, partly along the margins. 



Second cirrus also has unequal rami; the segments of both rami are cylindrical but 

 the longer one has eleven, the shorter only nine segments. 



Sixth cirrus (like the 3" 1 — 5 th ) not very elongated with nearly equal rami of 16 



89 



SIBOGA-EXPEDITIE XXXI a. 12 



