298 TAOR SKOOSBERO 



Sub-Genus Siphonostra n. sub-gen. 



Description: — Shell: — This is elongated and has a well-developed, beak-shaped 

 posterior process. The rostral incisvir is deep and narrow. Near the inner edge of the incisur there 

 are two niedial bristles situated close to each other. Posteriorly, within the posterior margin of 

 the shell, the list is not developed. Seen from inside, the posterior beak-like process appears 

 to have thin walls and to be constructed in such a way that wlien the two valves are close to 

 each other a rather wide tube, a siphon, is formed, a character which gives the sub-genus its 

 name. With rather strong calcification. The forms are of moderate size. 



First a n t e n n a: — This is comparatively short and moderately slender; with eight 

 joints; the proportions between the joints differ rather slightly from those given in the diagnosis 

 of the sub-familv; cf. the description of the sjDecies. The sensory bristle of the fifth joint has 

 a comparativelv small number of sensory filaments (always fewer than thirteen?). 



S e c o n fl a n t e n n a : — The p r o t o p o d i t e has a medial-distal bristle. E x o- 

 p o d i t e: The bristle of the second joint is rather strongly developed. Some of the natatory 

 bristles of the following joints have, in addition to natatory hairs, powerfid spines as well. 

 The third to the ninth joints have basal spines. The e n d o p o d i t e is reduced. (Similar 

 in the males as in the females? Cf. below that Cypridina hirsuta (!.^^'. MfLi.Kli may possibly 

 belong to this sub-genus.) The bristle of the end joint is long. 



Mandible: — P r o t o p o d i t e: The endite on the coxale is rather weakly bifur- 

 cated distallv, furnished with a rather powerful equipment of spines especially medially-distallv; 

 the spines onlv with rather a slight tendency towards arrangement in groups. This joint has 

 no bristle except the small one on the endite. Basale: Of the ventral bristles one d-bristle is 

 verv long, with numerous long secondary bristles at the middle arranged in irregular 

 groups and with short hairs distally; the other- ventral bristles on this joint are more 

 or less short and have short hairs or are bait'. This joint has three bristles dorsally. 

 Endopodite: The first joint has four bristles ventrally. The end joint has seven 

 bristles, of which the two middle ones are powerful and claw-shaped and of about the 

 same length and strength. 



Maxilla: — P r o t o p o d i t e: The coxale has distally a single bristle with short, 

 line hairs or almost bare. Proximally on the outside of the third (Midite there is a single bristle. 

 On the boundary between the l)asale and the first endopodite joint there are three bristles, 

 one close to the exopodite, one at about the middle of the inside of the jialp and one on the 

 anterior edge of the latter. Dorso-distally on the coxale there is a rather large and somewhat 

 lamelliform e }> i p o d i a 1 appendage. The exopodite is comparatively well 

 developed and lias close, fine, long hairs; it is not displaced distally. 'I'he e n d o p o d i t e is 

 very wide and of moderate length. 



Sixth I i m b: — The second exopodite joint is very short, broader than it is long, 

 furnished with rathrr few bristles: the posterior ones of these bristles are not strikingly larger 

 than the otliers. 



