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spine at the posterior corner of the right valve is always developed and in the speci mens
mvesti-gated by me it was bounded off by a decided angle from the posterior margin of the shell; cf.
fig. 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 by 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 faet 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 spine-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 thespecimensinvestigated by mebelonged to the type denoted by G. W. MÜLLER,
1906 a, as „Form a“. The médial 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 ekse 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 lengtli of this bristle
and the length of the whole limb is about 4 : 3, Somewhat distally of the middle this bristle has
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. Våvra, 1906, p. 38, gives the number as only 26; there are
28 in the figure given by this writer.) As G. W. MÜLLER 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
distally. (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 distally
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. Müller, not widened. The anterior
side of this bristle is quite bare. The b- and d-bristles are subequal, somewhat shorter than or
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. Müller
has pointed out, the b-bristle is furnished with a dense row of (about ten to twenty) rather short
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