\Q PEOCEEDINGS OF THE NATIONAL MUSEUM vol.76 



PLO at the lateral line. First PVO well below and anterior to the 

 second PVO.^^ 5 PO, the fourth elevated approximately to the level 

 of the upper PVO. Interspace between first and second PO enlarged. 

 VLO very low, its distance from the base of ventral fin only about 

 one-third of its distance from the lateral line. 4 VO, the second VO 

 elevated to the level of the VLO. SAO broadly angulate. First SAO 

 above the interspace between third and fourth VO^ somewhat nearer 

 to the vertical from the former. Second SAO above and behind 

 fourth VO and slightly higher than first SAO. Third SAO at the 

 lateral line, somewhat behind the vertical from second SAO. The 

 continuation of the line through second and third SAO passes well 

 behind the last VO. Only 4 Avidely spaced antero-anal organs, with 

 the interspaces gradually decreasing caudalwards. None of the an- 

 tero-anal organs elevated. 2 Pol., the upper at the lateral line, well 

 behind the vertical from the lower Pol., which is situated well behind 

 and somewhat higher than the last antero-anal organ. The anterior 



Figure 6. — Lampanyctus mexicanus Gilbert 



organs of the postero-anal series have unfortunately now become lost 

 in the type specimen, but four organs are found on each side on the 

 posterior part of the caudal peduncle in a continuous, horizontal 

 series along the ventral outline of the tail, ending at the bases of the 

 lower caudal rays. These four organs evidently must comprise the 

 posterior postero-anals and the anterior (lower) praecaudals and 

 their arrangement indicates these two series to be perfectly confluent. 

 The ultimate Pre is situated close to, but very distinctly above the 

 end of the lateral line. No intermediate organ was found between 

 this upper praecaudal and the above described posterior organ of 

 the ventral series (see figure), but there is a possibility that such 

 organs may originally have been present and have subsequently 

 become lost in the type specimen. This possibility is, however, not 

 confirmed by the original description, according to which there were 

 " six pairs of spots along the under side of tail, and three along base 

 of lower caudal lobe " (Gilbert, 1891, p. 52), when the specimen was 



"The pectoral fins have practically completely disappeared in this species and their 

 bases can therefore scarcely serve as orientation points for describing the positions of the 

 photophores. 



