26o DISCOVERY REPORTS 



SCYLIORHINIDAE 

 Scyliorhinus {Halaelurus) bivius (Smith) was not obtained at the trawUng stations. Five specimens 

 were obtained with ' Other gear ' at three stations in the western channels. 



SQUALIDAE 



Squalus lebruni (Vaillant) is very close to the familiar S. acanthias of the northern hemisphere. From 

 the material at Norman's disposal up to 1937 he judged that 'there appears to be only one species of 

 Spotted Spiny Dogfish in the southern hemisphere' (Norman, 1937, pp. 9-10). Dogfish are rare on 

 the Patagonian grounds, in strong contrast to their abundance in European seas. This would be a 

 helpful feature if long-lining for any of the more useful species were found practicable in the future. 

 They could of course be utilized in the same way as the northern species, but our records suggest 

 that they are far too scarce ever to form an appreciable part of the catch of a commercial fishery. 

 S. lebruni was not taken in ' Other gear ' ; records of its occurrence in the trawl are : 



WS90 I of 67 cm. length. WS791 B i of 66 cm., 1 150 g. 



WSg4 3 of 61, 62 and 64 cm. WS797C i of 66 cm., 1300 g. 

 WS218 I of 64 cm. WS853 I of 65 cm., 1200 g. 



These scanty records suggest that the species probably ranges over the whole of the shelf in summer, 

 and that it commonly attains a length of 2 ft. and a weight of some 2\ lb. 



SQUATINIDAE 



Squatina armata Philippi was not taken by the expedition, but Norman (1937, pp. lo-i i) provisionally 

 identified two Argentine specimens with this Chilean species, so that it may possibly occur within 

 the area of the trawling surveys. 



TORPEDINIDAE 



Discopyge tschudu Heckel. This species is known to range far north on both sides of South America, 

 but was only once taken by us : 



WS776 103 m. 4 $? specimens 



RAJIDAE 



The general distribution and depth relations of the species of this family taken by us have been 

 summarized, after the notes on individual species, in the form of tables and a figure dealing with all 

 the Elasmobranchs taken in the trawl (Fig. 18, p. 276). Measurements of disk width and many weights 

 were recorded, but owing to the scarcity of most of the species they are not sufficiently numerous to 

 repay statistical treatment. The individual records therefore refer only to numbers of specimens 

 taken. It is noteworthy that disk-width measurements made by Gunther and his colleagues in the 

 field show discrepancy with some of Norman's (1937) records, owing no doubt to shrinkage of pre- 

 served material. 



Rajaflavirostris Philippi. This species is morphologically very closely related to R. batis of British 

 seas and R. stabalifons of New England. It was widely distributed over the shelf in small numbers 

 rather more frequently in the northern region than elsewhere. In common with R. magellanica \t 

 favoured shallower waters than other members of the genus (Fig. 18), in spite of our difficulties in 

 sampling such a large area we can claim to have revisited most parts of the shelf at least three times 

 so that It is a remarkable fact that this skate was never found in the same place twice. Evidently it 

 must roam widely over the plain of the shelf (Fig. 8), and such behaviour is precisely the opposite of 

 that which Steven (1936) found in R. clavata. The young and adolescent stages of the thornback seem 

 nearly stationary, while even the migration of adults (Steven, 1932) is probably on a small scale 



