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widtli at about the middle and the anterior part of the shell considerably larger than the posterior
part; the side contours are rather decidedly concave just behind the middle, apart from which
they are evenly curved; the anterior and posterior ends are broadly pointed, the rostrum is
almost symmetrical. The shoulder vault is rather well developed and always well rounded.
The surface of the shell is bare and has a sculpture of the type reproduced by
G. W. Müller. Seen from inside: Selvage: This is in most cases smooth on the rostrum
and along the anterior margin of the shell and the anterior half of the ventral margin of the shell;
posteriorly it is exceedingly finely serridated. It has no spine-like process on the rostrum.
The glands are as described by G. W. MÜLLER; the left unsymmetrical gland has its exit just
at the posterior dorsal corner of the shell. There is an almost complete absence of medial glands
along the posterior margin of the shell (apart, of course, from the dorsal medial glands that are
well developed); the few that are found emerge with single pores a short distance inside the
margin of the shell. At the posterior dorsal corner there is a well developed hinge-socket and
hinge-tooth; see the accompanying fig. 4 (,^ — Ç).
First antenna: — The first joint is somewhat shorter than the second. The
boundary between the original second and third joints is scarcely or not at all developed. The
b-, d- and e-bristles are in most cases subequal, about one and a half times the length of this limb
or somewhat shorter. The e-bristle is armed with from eight to thirteen spines, according to
G. IV. MÜLLER; in C. Claus’s figures (1891 a) there are from seven to fourteen; on the specimens
investigated by me I counted from eleven to thirteen; these spines agréé with the type reproduced
by C. CLAUS, 1891 a. Proximally of the spines there are sparse and very short secondary bristles
on the anterior side of this bristle. These three bristles are bent at an angle, which is in
most cases a rather decided one, at about two-thirds of the way along them; they are not
widened distally and have no pad-like formations. G. W. Müller states that the b- and
d-bristles are bare; in the specimens investigated by me I was able in most cases to find
a few short, fine, distally pointing hairs about opposite the spines of the e-bristle. The
a-and c-bristles are of about the types shown in pl. XX, fig. 17, C. CLAUS, 1891 a. All the joints
are cpiite bare.
Second antenna: — Protopodite: In specimens with shells 0,8 mm.
long this measured about 0,4 mm. Exop odite: The proportion between the length of this
branch and that of the protopodite is about 10 : 16. The proportion between the length of the
first joint and the total length of the eight distal joints is about 10 : 4. The longest natatory
bristles are about a quarter longer than this branch. The first joint is bare. Endopodite:
First joint: The processus mammillaris has no distal verruca and is comparatively small. The
a- and b-bristles have short hairs. Second joint: The c-, d- and e-bristles are of about the same
relative lengths as in the figures 13 and 14 of C. symmetrica. The g-bristle is, as a rule, somewhat
longer than the protopodite, somewhat sword-shaped distally and furnished with exceedingly
short and fine hairs. The f-bristle is somewhat shorter than the protopodite, narrow, bare and
furnished with very short and fine hairs. Third joint: The clasping organs are of about the types
reproduced by G. W. MÜLLER, 1906a, pl. XXX, figs. 4—-7; they have rather decided transverse
creases distally. The h-, i- and j-bristles are subequal, about half the length of the g-bristle
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