16 DEEP-SEA FISHES OF THE ATLANTIC HASIN. 



The family, as thus defined, embi-aces Scyllium, Pristmriis, Stegostoma, Paratiri/llium, 

 Chiloscyllium, and related s'c'iH'ra. They are inhabitants entirely of the seas of the Old 

 World and Australia, none l)einj>' found in Ameriean waters. They are among the few 

 sharks which lay eggs invested in parchment-like cases, like those of the rays. 



KEY TO THE ATLANTIC GENERA OF SCYLLIOKHIXID.E. 



(Adapted from Giiiitbor.) 



I. Nasal and bucral cavities si>{)arate. 



A. Caudal fin witli upper odcrcs entirr. 



1. First ilorsal short, elevated ; anal origin in advance ol' siionil dorsal ScYi.l.lf)i;iilNrs 



2. First dorsal long, very low ; anal origin behind that of seeiunl dorsal PsErDOTKiACis 



B. Caudal tin with upper edges serrated Pkistmhus 



II. Nasal and buccal cavities confluent. 



C. Second dorsal fm marly opi)osite anal Ginclvmostoma 



Other genera, Stcnostoma, I'dniscj/lliiim, Chiloiiri/Uium, and CrosKorhiniis are peculiar to 

 oriental faunas. (IhH/lijMo.stoma is a shallow-water form, inhabiting warm wiiters. Few 

 species of Scyllium have been found at considerable depths. 



This family is nearly cosmopolitan, but has no representatives in either the western 

 Atlantic or in the eastern Tacitic, except a single Scyllium on the coast of Chile. 



SCYLLIORHINUS, Blainville. 



Scullwrkinus, Bi.ainvii.i.k (Jordan and tiilbert, Bull, xvi, U. S. Nat. JIns., 1883, 869). 



Sci/llium, CuviKR, Regne Animal, 1829, ii, 386.— MCller and Hexi.k, S. 15. I'lag., 3.— GOntiieI!, Cat. Fish. 

 Brit. Mns., viii, 400.— Day, Fish. Gt. Britain and Ireland, ii, 309.— Gii.1., Ann. Lye. Nat. Hist., iii, 107. 



Spiracles behind the eyes. Nasal cavities distinct from that of the mouth. Teeth 

 small, in many rows, usually with a central and one or two lateral cusps. Origin of anal 

 flu in advance of that of the second dorsal; upper edge of caudal not serrated. {Day.\ 



.SCYLLIORHINUS RETIFEIi, (Gauman). (Figures 14, 15.) 



Sci/lliiim rftifenim, CixRMAS, DnW.Mntt. Comp. Zool., 1881, vni, No. 11, 233.— Goode and Beax, Bull. Mus. 



Conip. ZoJil., vol. X, No. 5, 226. 

 ScuUiorlihiiis rctifcf, Jordan, Cat. Fish. N. A., 188.5, 5. 



Body moderate, portion behind the vent longer; head depressed, width nearly etjual to 

 its length in front of the spiiacles. IJistauce across the head at anterior angles of eyes, from 

 angle of eye to end of snout, between angles of mouth, between outer angles of nostrils, or 

 between angle of nostril and that of mouth, about e(|ual. Sliiipe of body similar to that of 

 S. canicula. Snout moderate, length from mouth less than the distance between the outer 

 margins of the nostrils. Nasal valves separated by an interspace of less than their \\ idth, 

 notreaching the mouth, somewhat folded, without a free cirrus, ^louth medium; the height 

 of the irregular arch formed by its outline is little more thiin half its width. Labial fold 

 on lower jaw extending nearly one-fourth of the distance to the symphysis; fold on upper 

 jaw rudimentary. Teeth snuxll, alike on ui)per and lower .jaws, bearing a sharp central 

 cusp, on eacu side of which are two smaller ones, several seiies in function at the same 

 time. No nictitating membrane. Spiracles small. Gill openings small, fourth and titth 

 over the base of the pectoral. Pectorals moderate, broad, short, anterior margins curved, 

 extremities rounded. Ventrals rather small, united for a short distance behind the claspers, 

 outer extremity broadly rounded, posterior angle acute. First dorsal much larger than the 

 second, about twice the length of its base in advance of the latter, extending forward above 

 the free portions of the ventrals, insertion very near the middle of the total length. Second 

 dorsal smaller than the anal, whic^h extends below the anterior half of its entire length, not 

 reaching the caudal. Oaudal not large, a shallow notch between its upper and lower 

 lobes, upper slightly indtiuted on its hinder margin. Scales of .shagreen small, unequal; on 

 those of the back there are three or five carina-, tlie median of which is prolonged into an 

 acute point. 



