40 Mr. G. T. Regan on the 



b. Dorsal fin-spines vestigial or absent ; teeth in the upper jaw- 

 erect, unicuspid, lanceolate or narrow triangular. 

 a. Caudal fin elongate ; teeth in the lower jaw erect, tri- 

 angular, finely serrated 9. ISaj mnorhinus . 



^. Caudal fin short and deep ; lower teeth not serrated, 

 *. Lower teeth oblique, with points strongly deflected 

 laterally ; dorsal tins subequal in length, the first far 



in advance of the pelvics 10. Sonmiosus. 



**. Lower teeth erect, triangular. 

 Dorsal fins subequal in length, the first very slightly 



in advance of the pelvics 11. Isistius. 



Second dorsal fin much longer than the first, which 



is not far in advance of the pelvics 12. Euprotomicrus. 



II. Snout produced into a flat blade, armed with a series of teeth on 

 each side ; no fin-spines. {Pristiophorincs.) 

 Five gill-openings on each side ; rostral teeth not 



serrated 13. Pristiophorus. 



Six gill-openings on each side ; larger rostral teeth 



with serrated posterior edges 14. Pliotrema. 



1. Centeoscyllium. 



CentroscyUmm, Mull. & Henle, Plagiost. p. 191 (1841), 

 Paracentrosci/lliuin, Alcock, Ann. i& Mag. Nat. Hist. (6) iv. 1889, p. 379. 



Tectli small, compressed, tricuspid or pentacuspid ; mouth 

 wide, arched. Each dorsal fiu preceded by a spine ; first 

 dorsal well in advance of the pelvics. Dermal denticles small, 

 si-attered, each with stellate base and a short, erect, pointed 

 cusp. 



Three or more species from deep water in the Atlantic and 

 Jndo-Pacihc. 



Synopsis of the Species. 



I. Upper lobe of caudal truncated posteriorly ; lower edge of the fin 



with a distinct posterior notch. 

 Origin of pectoral much nearer to end of snout than to 



origin of pelvics 1. fabricii. 



Origin of pectoral equidistant from end of snout and origin 



of pelvics 2. nigrv.m. 



II. Upper lobe of caudal produced and pointed posteriorly ; lower edge 



of the fin without distinct posterior notch 3. ornatum. 



1. Centroscylliuin fabricii. 



Spinax fuh'icii, Eeinhardt, Dansk. Vid. Selsk. Fcirh. iii. 1828, p. 16. 

 Ventroscyllium fabricii, Miill. & Henle, Plagiost. p. 191 (1841) ; 



Dumeril, Elasmobr. p. 449 (1865) ; Giinth. Cat. Fish. viii. p. 425 



(1870) ; Goode & Bean, Mem. Mus. Comp. Zool. xxii. 1896, p. 11 ; 



Collett, Rep. Norweg. Fish. Inv. ii. no. 3, p. 25 (1905). 

 ? Ce)it roscyllium (jrannlosum, Giinth. ' Challenger' Deep-sea Fish. p. 7 



(1880). 

 ? Cetitroaa/l/ium ritferi, Jord. k Fowler, Proc. U.S. Nat. Mus. xxvi. 



1903, p.' 635, fig. 6. 



