o 



iilS TAGE SKOGSBERG 



spine at the posterior conier of tlie right valve is always developed and in the sperimens nivesti- 

 i>ated by me it was bounded oft' by a deeided angle from the posterior margin of the shell; ef. 

 Hg. 3. When the shell is seen from the side the margin of the shell has, just ventrally of the 

 rostral incisur, a sort of spine-like process. This process is, as C. Claus has already pointed out, 

 formed bv the selvage, which is rather broadly convex at this point; when this part of the selvage 

 is seen from inside it is well rounded ; see fig. 4. Seen from inside: Apart from this the selvage 

 in this species is characterized by the fact that it is smooth-edged or only exceedingly finely serru- 

 lated along the anterior margin of the shell and the anterior half of the ventral margin of the shell ; it is 

 finely serrulated along the posterior half of the ventral margin of the shell and a short distance 

 of the most ventral part of the posterior margin of the shell; inside the remaining part of the 

 ventral half of the posterior margin of the shell the marginal spines of the selvage are somewhat 

 larger, but they never seem to be developed quite in the same way as in the accompanying 

 fig. 4 of C. symmetrica. The selvage has no large sjjine-like processes on the rostrum. There are 

 a few rather long, soft hairs scattered on the surface of the shell. With regard to the position 

 of the glands the specimens investigated by me belonged to the type denoted by G. W. MUlleu, 

 1906 a, as ,,Form a". The medial glands along the posterior margin of the shell are moderately 

 large; their exits are always simple, arranged in a distinct row running about half way between 

 the selvage and the edge of the shell or else somewhat nearer the latter, but not joined by any 

 distinct list. There is no distinctly developed hinge-socket or hinge-tooth at the posterior dorsal 

 corner of the shell. 



First antenna: — E-bristle: The proportion between the length of this bristle 

 and the length of the whole limb is about 4 : 3, Somewhat distally of the middle this bristle ha 

 two rows of proximally pointing spines along about a quarter of its length. The number of 

 spines in these rows seems to be subject to rather slight variation: about thirty or slightly 

 fewer were found in each row. (V. VAvRzV, 1906, p. 38, gives the number as only 26; there are 

 28 in the figure given by this writer.) As G. W. Mullki? has pointed out, all these spines, even 

 those situated most proximally, are close together. In most cases the spines in the two rows 

 are situated about opposite to each other, at any rate they do not distinctly alternate. All 

 these spines seem to be narrow and well pointed; those situated distally are rather short, about 

 as long as the thickness of the bristle at the place where they are attached, the others increase 

 fairly uniformly in length the more proximally they are situated, the most proximal ones being 

 rather long, from about three to five times as long as the distal ones. Just distally of these rows 

 of spines this bristle is furnished with a few short spines, which in most cases point somewhat 

 tlistally. (Most frequently they are of about the same type as the spines distally of the suctorial 

 plate on the e-bristle of C. elegans; cf. the accompanying fig. 15 of the latter species.) Just distallj' 

 of these spines this bristle is bent at a decided angle. The part of the bristle situated distally 

 of this knee is bare and. as has been pointed out by G. W. Muller, not widened. The anterior 

 side of this bristle is (|uit(> baie. The b- and d-bristles are subequal. somewhat shorter than nr 

 about as long as the e-bristle, often bent at a rather decided angle at about the corresponding 

 place to that in the last-mentioned bristle; they are not widened distally. As G. W. MUl-LKi-; 

 has pointed out. the l)-hristle is furnished with a dense row of (about ten to twenty) rather short 



s 



