198 Memoir Sears Foundation for Marine Research 



to inflate themselves with air, and which have widely distensible jaws provided with ver- 

 tical "accordion" folds in the corners, as well as very broad, flat heads. The majority of 

 recent writers have grouped these in the genus CefhaloscylUum. Fowler^^ has also pro- 

 posed the subgenus H olohalaelurus for two other species" that agree with the Swell 

 Sharks in lacking labial furrows, but which differ from them in having no ability to in- 

 flate and in having less distensible mouths, more slender trunks, shorter body cavities, as 

 well as in different relative sizes and locations of the fins. We propose to raise this sub- 

 genus to generic rank. 



The remaining species in which there is a well marked furrow around the corner of 

 the mouth reaching out onto both jaws are subdivisible by the relation of nostril to mouth, 

 size of the second dorsal relative to anal fin, and length of the interspace between anal and 

 caudal. 



In one rather sharply defined category of some thirteen named species, all from deep 

 water, the nostril is widely separated from the mouth and wholly distinct from the latter, 

 the anal is more than two and one-half times as long as the second dorsal, the interspace 

 between the anal and the caudal is very short or even reduced to a mere notch, there are no 

 folds below the eyes, and the snout is long and fleshy with very prominent mucous pores. 

 Fowler'" has recently distributed these species among three subgenera, based on the pres- 

 ence or absence of cirri on one or both margins of the nostril. But according to pub- 

 lished accounts and to our own examination of three members of the group, there is too 

 much intergradation in this respect for sharp separation. We therefore refer all of them 

 to the genus Apristurus Garman, 19 13. 



In a second category the anterior margins of the nostrils similarly fall considerably 

 short of the mouth and there is a labial furrow around the corner of the latter; but they 

 differ from Ap-is turns by having a much longer interspace between caudal and anal, a con- 

 siderably smaller anal relative to the second dorsal, and a well marked fold below the eye. 

 Although the twelve named members of this group {Halaelurus Gill, 1861) resemble 

 one another so closely that some reduction in the number of species is to be expected even- 

 tually. Fowler'^ divides them among two subgenera, Aulohalaelurus and HalaeluruSy 

 according to the lengths of the labial furrows, while Whitley has raised the former to 

 generic rank, besides proposing two new genera, Juncrus and Asymbolus^' But the differ- 

 ences between the several species of this group are so slight that we refer all of them to 

 the old genus Halaelurus. 



There remain only those species which fall with Halaelurus in most respects, except 

 for the anterior margin of the nostril, which more or less overlaps the anterior part of the 

 mouth, and except for a shallow groove which extends either from the nostril to the mouth 



18. Proc. Acad. nat. Sci. Philad., 8s, 1934: 235 ; Bull. U.S. nat. Mus., 100 (/j), 1941 : 4'- 



19. ScyUiorhinus functatus Gilchrist (Mar. biol. Rep. Cape Town, 2, 1914: 129) and S. regani Gilchrist (Mar. 

 biol. Rep. Cape Town, 2 [3], 1923 : 45, 46). 



20. Bull. U.S. nat. Mus., 100 (75), 1941 : 53. 21. Bull. U.S. nat. Mus., 100 i's), 1941 : 4'- 



22. Aust. Zool., 9, 1939: 229; Juncrus for Scyllium mncenti Zietz, 1908, and Asytnbolus for Scyllium anale Ogilby, 

 1885, both from Australia. 



