.^•W TAOE SKOOSltKlUl 



2) Of tht> six species of this jionus known from coldor sons (Arctic and Antarctic) fnui* 

 are characterized by iiaving these bristles broken off in okU'r leinaics. 



These facts indicate" that external, climatic factors have perhaps caused tliis pccnliai 

 convergence ** 



it does not seen\ impossible that in the case of species which ^re characteriz.ed by having 

 the natatory bristles of the second antenna imbroken throughout the whole life the females 

 are impregnated several times. The statement made by G. W.- MtlLI.KK, 1894, p. 174, according 

 to which /'/(. f Pit.) interpuncta lays at least two lots of eggs, seems to me t(}''support this. 



Genus Philomedes W. Lilljeborg. * 



Cypridina (part.) auto rum; c g. W. Baihh, 1850 a and Fn. Mi'i.lkh, 1870. 

 Asterope, S. Fischer, 185.5. Philomedes (= S) + Cypridina (= $ and juv.). W . LlLl*KBORG, 

 1853. Philomedes (= c?) + Bradyeineius (= ? and juv.), G. (). Sars, 1865; G. S. Brahv,' 

 1868 b and 1871. Philomedes (= J, $ and juv.) auto rum; e. g. G. 0. Sars, 1869 

 and 1887; G. \V. .AFCller, 1894; G. S. BiJADV and A. M. XoliMAX, 1896. Philomedes (part.), 

 (4. W. Ml'LLER, 1912. 



With regard to the relation of Pleoschisina and Tetragonodon to this genus cf. above 

 the remark below the sub-family. 



Diagnosis: — Cf. G. 0. Sars, 1887, p. 45 and G. S. BRAin' and A. M. Norman, 1896, ]i. 65.3. 



Description: — Shell: — This has marked sexual dimorphism. 



Female: — The shape of the shell varies rather considerably. The rostral incisur 

 is of a somewhat varying type, but is most frequently deep and narrow. The sculpture of the 

 surface seems in most cases to be very weakly or even not at all developed; in some cases, 

 on the other hand, it is very powerful. Seen from inside: The part of the shell between 

 the list and the posterior margin of the shell is flattened and not curved in like a siphon, so that 

 the two valves are near each other at this part when the shell is closed ; only in exceptional cases 

 is there any indication of a siphon: (cf. the description of Ph. ( Scieroconcha) AppeUofi). 

 Medial bristles: These had in the species investigated by me almost exactly the same type: 

 On the rostrum there was a row running at some distance from and almost parallel to the ventral 

 part of the anterior margin of the rostrum sometimes continuing a little way along the anterior 

 margin of the rostral incisur. Most of these bristles were rather long and finely feathered; 



* It may be pointed out that Ph. (Ph.) orbicularis, a species from the Antarctic, described by G. S. Brady, 



which is certainly very closely related to Ph. (Ph.) rotunda, has, according to this author's drawing, 1907, pi, I, fig, 8, 



long unbroken natatory bristles on the second antenna; there is, however, no information as toVhether the female from 



which the antenna that is reproduced was taken had eggs in the brood chamber or if it was still in the plankton stag<\ 



•• See R. Hesse and F. Dofi.f.in, ,.TitTbau und Tierleben", 1914, II, p. 876. 



