the posterior part of the maxillare. In the lower jaw, similar denticles 

 occur along the entire length of the upper margin of the dentary. The 

 narrow, arcuate pterygoid is placed above the upper jaw. The keratohy- 

 ale with numerous radii branchiostegii occurs an the prolongation of the 

 maxillare. 



The deep operculum (Fig. 5) is the best developed of the bones 

 of the gill covers. The preoperculum occurs as an extremely narrow, 

 elongated bone without spines. Another, similarly narrow bone, can 



front. 



parsph. ^ 



prmax -~..^ 



prorb.-- 



sprmay. 

 brst. 



Fig. 5. Polyipnus sohnioviensis n. sp., skull (after specimen No. 124. Os); luminous 



organs reconstructed after specimens Nos. 124. Or. and others ca. x 10. 



abd. abdominal organs, brst. branchiostegal organs, cl. cleithrum, cor. cora- 



coideum, dent, dentary, front, frontale, intop. interoperculum, isth. organs on 



the isthumus, krthy. keratohyale, max. maxillare, op. operculum, prorh. preorbital 



organ, suhop. subopercular organ, parsph. parasphenoideum, prop, praeoperculum, 



prmax, praemaxillare, ptr. pterygolideum, Q — quadratum, r. hr. radii brianchios- 



tegii, sprmax. supramaxillare, sprlc. supracleithrum. 



15 



