3 i2 DISCOVERY REPORTS 



barb and all but the first, which is more or less upright, antrorse. Palatine with about twelve smallish, 

 pointed teeth. The lingual teeth (see text-fig. 3 a') more than any other feature, show that this must 

 be a young scopelarchid. 



When caught the fish was almost transparent, the only colour being the black pigment of the eye 

 tube. The body-wall is quite transparent, the internal organs, gut, liver and mesenteries, showing 

 clearly. The muscles associated with the base of the pelvic fins are moderately dense, but over the rest 

 of the body wall there is but a thin muscle-layer, which becomes less and less easy to distinguish as one 

 works upwards from the pelvics. Along the mid-ventral line from the head to the pelvic fins, there 

 is a sharp hyaline division between the musculature of each side of the body wall. 



Relationships. Following on this section, reasons will be given for recognizing two genera of scopel- 

 archids, Scopelarchns Alcock and Neoscopelarchoid.es Chapman. One of the features distinguishing 

 them is the relative position of the dorsal and pelvic fins. In the larval specimen from station 3051, 

 the origin of the dorsal fin lies behind that of the pelvic fins, a characteristic of the genus Neo- 

 scopelarchoides; hence the larva may be presumed to belong to this genus. It also has the full comple- 

 ment of principal caudal and pelvic rays (and presumably of dorsal, anal and pectoral rays), and at this 

 stage there is unlikely to be much shift in the relative positions of the dorsal and pelvic fins. But it 

 cannot be fitted with certainty into any of the four known species. In numbers of fin-rays it is closest 

 to N. dubius and it also agrees with this species in the number of body segments before the origin of 

 the anal fin (the remaining myotomes cannot be counted with certainty). The larva has thirty-five 

 pre-anal fin myotomes, and N. dubius has thirty-five pre-anal fin lateral line scales and vertebrae. 

 N. elongatus has 33-35 pre-anal fin segments but the anal rays (26-27) are more numerous than those 

 of Benthalbella. 



I have already drawn attention to the fact that N. dubius sp.n. may prove to be the adult of a larval 

 form, Benthalbella infans described by Zugmayer in 191 1. Zugmayer's young fish and the Discovery 

 larva are very similar, the only difference being in the number of anal rays (17 compared with 22). 

 A number of other specimens, previously recorded, also nearly resemble them : 



(1) The fish figured in Murray and Hjort (1912) on p. 746 and labelled 'New fish resembling 

 Dysomma ' (sic). The drawing shows nine dorsal and twenty or twenty-one anal rays. 



(2) Two Benthalbella larvae from the Bay of Cadiz (Schmidt, 1918). Fin-ray formula: D. 9-10, 

 A. 21-22, Pect. 26, Pv. 8-9. 



(3) Two Benthalbella larvae from Madeira and one from the Azores (Roule and Angel, 1930) 

 which were regarded as young stages of Omosudis lowei. Their Plate III, figs. 75 and 76 show a 

 fin-ray complement of D. 8-9, A. 20. 



(4) Three post-larval Benthalbella from the Strait of Gibraltar (Nybelin, 1948). Fin-ray formula: 

 D. 9-10, A. 20-22, Pect. 27, Pv. 9. 



The distribution of these larvae may be seen in the chart, fig. 4. 



It would thus seem probable that the Discovery larva and all those listed above belong to one 

 species of Neoscopelarchoides. If this is so, the species has a fin-ray complement of D. 9-10, A. 17-22, 

 Pect. 22-27, Pv. 8-9. N. dubius comes very close to this; and it may be concluded that either these 

 remarkably large larvae are the young of N. dubius or of an unknown, closely-related species. 



RELATIONSHIPS AND SYNONYMIES OF THE GENERA 



Considering in chronological order the genera that have been included in the Scopelarchidae, 

 Dissomma Brauer (1902) is clearly synonymous with Scopelarchus Alcock (1896), for S. guentheri 

 Alcock and Dissomma anale Brauer are either very closely related or belong to the same species. 



