263 



and traces of crests for the attachment of the tergal depressor muscle can be seen near the 

 basi-carinal angle of the valve. 



The study of the structure of the animal contained within the shell has given the 

 following results : 



Buccal process not very prominent; at its side the cirri of the first pair are attached; 

 la'brum (PI. XXVII, fig. 5) widely and also deeply notched, with three small triangular teeth 

 on each side of the notch. Pal pi broad, rounded, with numerous and not very long, partly 

 curled hairs disposed on the inner surface and along the upper margin. 



Mandibles (PI. XXVII, fig. 6) with five teeth and the inferior angle not distinctly 

 separated from the fifth. Distance between tips of first and second teeth slightly surpassing 

 that between those of second and third teeth. The third tooth is the most massive, the fourth 

 and fifth are smaller than the others. The second and third teeth are laterally doublé. 



The maxilla (PI. XXVII, fig. 7) has a straight edge; below the two larger upper 

 spines there is a rudimentary notch; on the part of the edge below this notch 7 to 8 spines 

 are disposed, one or two of which are almost as strong, and only a trifle shorter than the 

 two upper ones. 



The ou ter maxillae (PI. XXVII, fig. 8) are bilobed; the inner lobe is small, the 

 outer rather broad and of an oval shape. Numerous hairs are disposed along the inner margin 

 and on a part of the surface, towards the interior of the mouth. 



Cirri. Those of the first pair have very unequal rami of twelve and six segments. 

 In both rami hairs are disposed in dense groups at the front side on the upper half of the 

 surface of each segment. That part of the surface of the segments of the shorter ramus on 

 which the hairs are disposed is slightly protuberant. 



The cirri of the second and third pair have about the same structure, the latter 

 being only slightly longer than the former. The rami of the second cirrus have 6 and 8 seg- 

 ments, the longer ramus having its segments slightly more protuberant than the six segments 

 of the shorter. The hair-like spines on the segments of the 2 nd cirrus are much longer and 

 form denser bushes than those of the 3 ld cirrus. The latter has 7 segments in the shorter 

 ramus and 8 in the longer. 



The cirri of the 4* to 6 th pairs have the rami rather short. Those of the 6 ,h pair 

 have eleven and twelve segments, the first of which is very long, the following being about 

 two and a half times as long as broad. The number of pairs of spines on the inner face 

 of each segment is three, the first or lowest pair being extremely small. 



The penis is extremely long, tapering towards the extremity, with delicate hairs scat- 

 tered over its suriace and a few more disposed near the extremity. 



The straight project ing point at the dorsal basis of the penis is well developed ; 

 it is slightly curved, but its apex is not pointed, but blunt. 



One of the specimens I examined was furnished with eggs. As far as could be made 

 out, they were united into a cluster (and only in one) and did not form true lamellae. The 

 eggs are not very numerous (about 60 to 80 altogether) and relatively small : they measure 

 only 0.27X0-14 mm. 



i3S 



