6 DKEP-SEA FISHES OP THE ATLANTIC 15ASIN. 



KEY TO THE ORDERS OF SELACHII. 



I. Trunk more or less cylindrical, snulually t:iporing into the tail; gill openings lateral . .. .Sqi'ali (Sharks) 



II. I'rtmk depressed (ill typical gcnei-a the highly devcloi)ed pectoral fins loruiiug a broad flat disk) ; gill 



openings veutral RaI/E (Skates and Rays) 



Order SQUALL 



The Sharks. 



Sehichiaiis, with body more or less oyliiulrical (sometimes miuii dejiressed aiiteiiorly), 

 gradually attenuating into the tail. Branchial openings lateral, slit-lilve, 5-7 in number, either 

 entirely in front of or entirely behind the peetoral, opening over their bases. Pectorals 

 moderately developed, distinctly differentiated from the sides. 



KEY TO THE DEEP-SEA FAMILIES OF SQUALL 



I. Anal fin lacking. 



A. No spines in front of dorsal fins SCYMNORHINID.-E 



B. Each dorsal fin preceded liy a spine Spinacid.k 



II. Anal tin iiicsent. 



A. Dorsal lins two, withinit antecedent spines, the first al)Ove or liehind the veutrals Scylliid.e 



B. Dorsal fins two, without spine.s, the first in advance of ventrals; caudal crescentic, with a keel on 



each side of its stem; gill opening.s enormous Cktoriiinid.-e 



C. Dorsal fin single, without spine; caudal without notch posteriorly Oulamydoselaciiid.e 



In this key only those families are included representatives of wliich have actually 

 been taken at great depths. Other forms, such as ISdaclw intixima, jirobably sink lielow the 

 huiidred-fatlionis limit at times. Oanestrini records as living " /« Inoijhi prufoHili,^^ in the Med- 

 iterranean, Kotidanun (jrixeus, Heptancliun cinereus, Selache maxima, and Carcharodon Ron- 

 delctii. Spina.r nujer, however, tSci/mnn.s livliia, nml lAcmaroiis roxfrafns, which dwell "« 

 f/rande profoiidita,'" appear to be the only Mediterranean forms entitled to admission in this 

 list, except perhaps Genirophorm yranulosuH, which it may be strays in from the deeps of the 

 Atlantic, as far east as Sicily, and Erhinorhinus. 



Family SCYMNORHINID.^. 



Scymnidcp. Gill, .Johnson's Cyclopa-dia, iv, 158.— Jordan and Gilbert, Bull, xvi, U. S. Nat. Mus., 1883, 13. 

 Spinaeid(v (in jiart) Gunther, Cat. Fish. Brit. Mus., viii, 425-429. 

 Scymnorhinida:, Gill, ms. 



Scymnoid selachians, without anal fins and with spineless dorsals. Scales generally 

 developed in the form of shagreen or fine bristly si>iiies; head oval, depressed; eyes 

 without nictitating membranes; nostrils with a simple anterior tag; mouth inferior and 

 .somewhat arched; teeth with trenchant edges; branchial apertures five, in advance of the 

 pectorals; dorsals two, siiineless, the first in advance of the ventrals, the second far behind; 

 anal lacking; pectorals rather small ; ventrals placed far back. {Gill.) 



KEY TO THE GENERA OF SCYMNID.E. 



I. First dorsal in advance of ventral. Lower teeth erect, triangular Scymnorhinus 



A. Dorsal fins similar in size. Lower teeth oblique, quadrate, with horizontal cuttiug edges.. SoMxiusus 

 I?. Second dorsal longer than first. Upper teeth small, conical. Lower teeth larger, triangular, some- 

 what o)ili<iuc [Eri'UOTo.MK in s. — Indian Ocean.] 



II. First dorsal opposite veutrals. 



C. Teeth ei|ual in both .jaws, large, very obli(iue, eacli with several smuU cusps. .Skiii witli irregularly 



phiced round osseous tub(^rclcs and ]irickles EciiiNdiuiixr.s 



D. Low<'r tei'th much hirger than u)i|icr, i^rect, not serrated. Skin granular. 



[IsisTirs. — South P.acilic and Gulf of (Jninea.] 



This family is not common in .Vmericau M'aters. Of the three genera occurring in the 

 Atlantic, one, Scymnus, has been found only in the Mediterranean and the adjacent parts of 



