Sliiilics on inaiinii Oslincods 170 



Sub-Family Cypridininae. 



S u b - F a m. Cypridininae, 0. W. MliLLER, 1912, p. 8. 



Description: — Shell: — Sexual dimorphism, in most cases, weak, sometimes scarcely 

 noticeable or even entirely undeveloped. — The type of shell varies very nmch. The s u r- 

 f a c e sculpture is, in most cases, not at all or else rather weakly developed. Seen from 

 i n s i d e: The part of the shell between the list and the posterior margin is flattened in most 

 forms, not curved inwards in the sliape 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 Siphonosira, 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: — Witli rather considerable 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 may even 

 have only six owing to a more or less complete imion 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 following are the usual proportions (the figures are from measurements of 

 Cypridina [DoloriaJ levis): 



I ;]; II 1; III h IV '^,; V 1; VI |; VII |; VIII 0,5. 



\Mien 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 nearly 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 

 here seems, however, not to be quite general; the genus Crossopliorus, for instance, is an 

 exception (cf. G. W. MOLLer, 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 anteriorl_y-distally and one posteriorly-distally. 

 All these bristles, like the single bristle on the original sLxth 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 jt)int is always very 

 powerfully developed; its proximal part is strongly annulated, the annulation becoming naore 

 and more fine distally and sometimes quite disappearing, in which case the end of the bristle 

 seems quite hyaline; the filaments of this bristle are also finely annulated or distally even quite 

 hvaline; distallv 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. Iti of Cypridina (Vargula) norvegica, in other words one is 



