Family Cypridinidae. 



Fam. Cypridinidae. Li S. Brady and A. M. Nohman, 1896, p. 638. 

 Sub-Fam. Cypridininae-i-SMh-Y&m. Philomedinae (part.), G. W. MOlleh, 19U6 b, p. 12. 

 ' „ „ „ „ „ „ „ ,, ., n 1912, pp. 8, 24. 



Description: — Shell: ^ With or without sexual dimorphism. — The rostral incisur 

 is in most forms rather deep, in others, on the contrary, more or less shallow, but is never, 

 however, quite absent; the upper lip of the incisur does not grow over the under one. The selvage 

 varies in type, but is always lamelliform and most frequently well developed both on the 

 rostrum and along the greater part of the ventral margin of tlie shell; it runs about parallel 

 to and somewhat within the free edge of the valve. The list runs from the rostral incisur in 

 an even, unbroken bow along the ventral and posterior edge of the shell, and finishes at the 

 back near tlie hinge of the shell (exception among the hitherto known forms: Siphonostra and 

 Cypridinodes, cf. below, the diagnoses of these sub-genera); it is sometimes narrow throughout 

 its vvliole length or else somewhat broader at the back; the distance from the list to the edge 

 of tlie shell is, on the average, somewhat greater along the back edge of the shell than along 

 the ventral edge. The valves, as in all forms belonging to the s t r a cod s, are joined 

 along less than half the periphery; in only a single one of all the genera so far known, the genus 

 Gigmttocypris (cf. below, the diagnosis of this genus) are they joined along more than half the 

 periphery of the valves. The males never have a ring of hairs round the posterior part of the shell. 



First antenna: — This has more or less strt)ngly marked sexual dimorphism. 

 — The sensory bristle of the fifth joint developed very variously, sometimes entirely absent 

 in the females. The original sixth joint has always only one bristle, placed distally-mediaUy. 

 Distally this limb has seven to eight bristles, three to four of which are ])robablv to be 

 considered as belonging to the original seventh joint and four to the original eighth joint. The 

 anterior bristle on the original seventh joint (a-bristle, cf. below, the terminology for the sub- 

 family Cypridininae) is never developed i!i the sliupe of a claw. 



S e con d a ii t e n n a: — In a number of forms this limb is characterized by sexual 

 dimorphism, in others it is almost or entirely without it. — E n d o p o d i t e: In the female 

 most frequently rather small and weak, sometimes even more or h'ss entirely reduced. In the 

 male this brancli is sometimes of the same type as in tlie female, sometimes it is developed as 



