56 Bulletin 4J, United States National Museutn. 



40. CENTROSCYLLIUM, Miiller & Henle. 



CentrosojUium, Mi'llek A Henle, Systomatischo BescUreibung dor Plagiostoinen,191, 1838, (/a6- 

 ricii). 



Teeth equal in both jaws, very small, straight, pointed, each with 1 or 

 2 smaller cusps on each side at base; mouth crescent-shaped, with a 

 straight, obli(iue groove at its angle; spiracles moderate; gill openings 

 rather narrow; dorsal fins small, each with a strong spine; the second 

 dorsal entirely behind the ventrals. One species, in the Arctic Seas. 

 {liivrpov, spine, gkvXXioi', Scylliiim, an allied genus, from oKvATiU, to rend 

 or tear to pieces.) 



75. CEN'TROSCTLLIUm FABRICII, (ReiubarcU). 



Body covered with minute stellate ossification ; dorsal fins short, with 

 strong spines; second dorsal behind ventrals; color nearly black; Green- 

 land Seas, southward in deep water ; occasionally taken off' Gloucester and 

 off' the Nova Scotia Banks. (Named for Otho Fabricius, a Danish natural- 

 ist, the first to study the fishes of Greenland.) 

 Spinax fahricii, Beinhahdt, Dansk. Vid. Selsk. Forh., 1828, 111, xiv, Greenland. 

 Cenlroscyllinm fahricii, Gunther, Cat., viii, 425, 1870. 

 CentrosctjlVmm fahricii, Jobdan & Gilbert, Synopsis, 16, 1883. 



Family XIX. DALATIID^. 



(The Scymnoid Sharks.) 



Sharks with no anal fin and with 2 dorsal fins, each without spine ; 

 fins all small : gill openings small, entirely in advance of pectorals ; mouth 

 but little arched; a long, deep, straight, oblique groove on each side of 

 it ; spiracles present. Oviparous, the eggs without horny case (at least 

 in Somniosus). Vertebi'jB cyclospondylous. The absence of dorsal spine 

 chiefly distinguishes this family from the Squalid/E, of which these are 

 somewhat degenerate allies. Genera, 5; species, about 10, mostly of the 

 North Atlantic, some of them reaching a large size. (SPiNACip.E, part, 

 (iunther, Cat., viii, 425-429.) 



Somniosinje: 

 a. First dorsal niucli in advance of ventrals. 



h. Upper teeth narrow, the lower quadrate, with a horizontal edge ending in a point 

 directed outward ; body very robust, the fins very small, the dorsals about equal ; 

 skin moderately rough. Somniosus, 41. 



41. SOMNIOSUS, Le Sueur. 



Somnioms, Le Sueur, Jour. Ac. Nat. Sci. Phila., 1818, i, •i21.{hrevipinna=microceplmlwi). 

 Leiodon, Woon, Proc. Bost. Soc. Nat. Hist, n, 174, 1847, {echinalum=microcei>hah(x). 

 Lxmargus, MtJLLER & Henle, Plagiostomen, 93, 1838, {borealis=microcephalus). 

 Rhinoacymnm, Gill, Proc. Ac. Nat. Sci. Phila., 1864, 264, (roslratus). 



Body thick and clumsy; mouth transverse, little arched, with a deep, 

 straight groove running backward from its angle; nostrils near the 

 extremity of the snout ; jaws feeble; teeth in upper jaw small, narrow, 

 conical ; lower teeth numerous, in two or more series, the point so much 



