ison of young forms with genus Idrissia Aramb. reveals a rather close 

 resemblance in the shape of body. 



The other evolutionary line of the Gonostomidae may possibly also 

 be traced back to the Cretaceous, from the genus Idrissia Aramb. to 

 the living representatives of Ichthyococcus Bonaparte. These supposi- 

 tions cannot be accepted until the osteology of the genus Ichthyococcus 

 is adequately known, and remains of Idrissia — with the luminous 

 organs preserved — are discovered. 



Family Sternoptychidae 



Genus Polyipnus Giinther, 1887 



Polyipnus sohnioviensis n. sp. 



(Figs. 5, 6; PI. II; PI. Ill, Fig. 1) 



Diagnosis. 31—33 vertebrae (of which 19—20 are caudal), P 10, V 7—8, 

 DIG— 11, A18— 20, C5— 6— 10— 10— 5— 6. Maximum body depth quite close 

 to the head; no spines before the dorsal fin. The predorsal area represents 

 48 — 56 percent of the body length without the caudal fin. The anal fin 

 begins below the last rays of the dorsal fin or just beyond th-em. The 

 luminous organs in distinctly differentiated groups: subcaudal, anal, 

 preanal and abdominal. The group of supra-abdominal organs consists 

 of 4 detached photophores. 



Material. 70 skeletons showing body-outline and traces of photo- 

 phores; of these, 26 specimens are complete and have served for the 

 computation of the variability range of the body dimensions. The col- 

 lected material also contains 7 heads broken off from the body, most 

 likely conspecific. Only one headless body has been found. Specimen 



Table 3 



Dimensions of P. sohnioviensis r 



1. sp. ( 



in mm) 







Dimensions 



Holo- 

 type 



Paratypes 





49. Os. 



124. Os. 



260. Os. 



232. Os. 



157. Os. 



128. Os. 



Length of body without caudal fin 



23.1 



22.9 



21.9 



18.0 



33.4 



29.9 



Depth of body immediately behind head 



9.5 



9.2 



9.5 



6.7 



9.6 



8.1 



Depth of body at beginning of dorsal fin 



9.4 



9.1 



8.5 



— 



8.2 



6.5 



Depth of body at beginning of anal fin 



6.4 



7.1 



7.4 



— 



6.5 



6.1 



Length of head to posterior margin of 















operculum 



8.5 



7.6 



7.6 



6.2 



10.7 



10.3 



Depth of head 



10.1 



10.3 



— 



7.9 



10.4 



9.0 



Predorsal area 



12.3 



12.3 



12.0 



— 



12.5 



16.7 



Length of caudal fin 



6.6 



7.7 



6.0 



5.5 



8.5 



7.9 



13 



