contained by the particular groups. The writer's description of the 

 luminous organs is based on the nomenclature of Schultz (1938). 



After Brauer (1908), two fundamental types of luminous organs 

 may be distinguished in the living representatives of the Sternopty- 

 chidae: 



(1) single photophores which are broad and laterally strongly flat- 

 tened, and 



(2) groups of photophores, formed by the fusion of several luminous 

 organs. 



Fossil photophores, only partly preserved, are recorded among 

 remains of Argyropelecus hullockii David (David 1943). In representa- 

 tives of Polyipnus sohnioviensis, the writer has encountered traces of 

 pigment which are the vestiges of the next luminous organs. 



Skull: (1) a detached preorbital organ, placed below the level of 

 the parasphenoid in front of the orbit; it is satisfactorily preserved on 

 specimen 156, Os and certain others; (2) a detached subopercular organ, 

 best seen on specimen 56. Os., lying at the back of the head in the 

 prolonigation of the branchiostegal photophores; (3) a group of bran- 

 chiostegal organs — the faintest traces, frequently fragmentary — most 

 readily discernible on specimen 56. Os. and situated in the fore part 

 of the head, near the keratohyale; (4) a group of organs on the isthmus; 

 this is a fairly large group somewhat obliquely oriented within an area 

 from the quadratum. to the pectoral fins. 



The trunk: (5) group of abdominal organs; this is the largest 

 group of low photophores, which begins before the pectoral fins and 

 terminates at the base of the ventral fins; (6) a group of supraabdominal 

 organs, consisting of 4 distinct, large, detached photophores which lie 

 above the last photophores of the abdominal group; (7) a group of 

 preanal photophores, which lie before the beginning of the anal fin 

 and constitute a clearly delimited, deep group which has been adequate- 

 ly preserved in all individuals; (8) a group of anal photophores, longer 

 than the preanal group, beginning between the 8th and the 9th 

 rays of the anal fin; the detectable traces reasonably suggest the 

 occurrence in this group of 6 — 8 detached photophores; (9) a group of 

 subcaudal photophores, lying far toward the rear of the body and 

 reaching to the base of the first side rays in the lower lobe of the 

 caudal fin. 



The body ^ of the individuals here investigated is bare, devoid of 

 the traces of scales. Two fairly large groups of minute spots of pigment 

 (Fig. 6), distributed near the caudal fin and in the central part of the 

 body, have been observed above the vertebral column of certain spec- 



19 



