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Sub-Family Cypridininae.
S u b - F a m. Cypridininae, G. W. MÜLLER, 1912, p. 8.
Description: — Shell: — Sexual dimorphism, in most cases, weak, sometimes scarcelv
noticeable or even entirely undeveloped. — The t y p e of shell varies verv much. The s u
r-f a c e sculpture is, in most cases, not at all or else rather weaklv developed. Seen from
insid e: The part of the shell between the list and the posterior margin is flattened in most
forms, not curved inwards in the shape of a siphon, so that, when the shell is closed, the two
valves are here pressed rather close to each other; an exception to this last rule among the forms
so far certanly known is the sub-genus Siphonostra, cf. below; to judge from the descriptions
it seems, hoiwever, to be possible that other forms as well are distinguished by a similar
pecu-liarity. Hinge very seldom with teeth.
First antenna: —■ With rather considérable sexual dimorphism.
Female: — Most often with eight joints, less often with seven owing to a more
or less complete union of the fifth and sixth or the seventh and eighth joints, or it mav even
have only six owing to a more or less complete miion of both the fifth and sixth as well as the
seventh and eighth joints. The proportion between the joints seems to be subject to but slight
variation; the folio wing are the usual proportions (the figures are from measurements of
Cypridina [Doloria] levis)-.
I 17. u 23. m li. i y 10. y L. Yl -
1 14? 11 13’ AAA 3 ? A> 10? ’ 6’ ’ 1 3
VII y; VIII 0,5.
When in the descriptions of the forms belonging to this sub-family no special information
is given as to these proportions the form in question agrees pretty nearl v with the example
given above. All the forms of this group investigated by me showed the same number and also
almost exactly the same situation of the bristles. All the characters of the bristles given below
are to be taken as common to all these forms. To judge from the literature, the type described
liere seems, however, not to be quite general; the genus Crossophorus, for instance, is an
exception (cf. G. W. MÜLLER, 1906a, pi. XXXIV, fig. 4). The second joint is quite without
bristles; the third joint has two bristles, one placed anteriorly and one posteriorly-distally; the
fourth joint also with two bristles, one placed anteriorly-distally and one posteriorly-distally.
All these bristles, like the single bristle on the original sixth joint (see above, p. 174)
are simple, pointed, annulated, naked or with only short and usually very fine secondary hairs;
they are comparatively short or of moderate length and, as far as I have observed, never
differentiated into specific sensory organs. The sensory bristle of the fifth joint is always very
powerfully developed; its proximal part is strongly annulated, the annulation becoming more
and more fine distally and sometimes quite disappearing, in which case the end of the bristle
seems quite hvaline; the filaments of this bristle are also finely annulated or distally even quite
hyaline; distally both the principal bristle and the filaments are finely rounded and furnished
with a short, fine sensory hair. The original seventh joint has three distal bristles, situated
in about the position shown in fig. 16 of Cypridina ( 1 argula) norvegica, in other words one is
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