ADDENDA 7—. CARCnAEIIDiE CARCHARIAS. 967 



very short, its base strai*;bt, slightly oblique. Size much less than 

 that of Mold rotunda. Pelagic; occasional ofi'our Atlantic coast. 



{Tctrodoti triDicaluK Hot:;. Vet. Ak. Nya Ilaiull. vi, 2, IIG: Orthagoriseus oUongus 

 Bloch & Scliu. IdOl, 511: Orthagorixcus Iruiicatus Giiutber, viii, 319.) 



Family BDELLOSTOMATID^. 



The genera Hcptatrcma and PoUstotrema m.iy be recognized as con- 

 stituting a faiiiilj' {Bdellostomiflw Gill) distinct from Myxinidw. 



Page VI. We are indebted to Professor Gill for the following outline 

 of a proposed subdivision of the SquaU. 



The existing Squali appear to be naturally divisible into four subor- 

 ders, which differ, so iar at least as the first three are concerned, in 

 many iniportaiit respects. They may be briefly diagnosed as follows: 



I. OPISTHARTHRI or CYCLOSPONDYLI. 



Squall with the palato-qiuulrate apparatus articulated or connected ■with the post- 

 orbital processes of the skull; the mouth inferior; branchial apertures in increased 

 nuiuber ((3 or 7); only one dorsal fin. The Xotidauidcv alone exhibit these peculiarities 

 in the existing fauna. 



II. PROARTHRI OR ACRODONTA. 



Squali with the palato-quadrate apparatus articulated by an extensive surface with 

 th;^ preorbital region of the skull ; the mouth subterminal and the forehead declivous. 

 The HeterodoniUlw are the only living representatives. 



III. ANARTHRI OR GALEI. 



Squali with the jialato-quadrate apparatus not articulated with the skull; the den- 

 ti^erous portions moderately developed; the mouth inferior. All the living sharks 

 except the Sqtiatt)iida; HcUrodoniidw, and Notldanida', belong to this suborder. 



IV. RHIN^. 



Squali with the jialato quadrate apparatus not articulated with the skull; the den- 

 ti;;erous portion advanced forwards; the mouth terminal; and the pectorals with en- 

 larged anterior l)asal lobes which are separated by notch-like spaces from the branchial 

 region. The family oi Squatinidiv is the only existing family of this suborder. 



Page 22, etc. The following brief "key" will jierhaps fiicilitate the 

 identification of the species of Carchai m.v, which are at present known 

 from our Atlantic coast: 



a. First dorsal far behind pectoral. (Carcharias) Glaucus 



au. First dorsal close Ixhind pectoral. 



b. Upper teeth oblique, deeply notched on outer margin. {Platijpodon Gill.) 



OnscuRUS.. 

 hh. Ui)per teeth triangular, suberect, scarcely notched on outer margin. {Eulauiia 

 Gill.) 

 c. Snout moderate, its length, from moutli, about equal to breadth of mouth. 



GaciifLKUS. 

 cc. Snout very short, its length much less than breadth of mouth Platvodon. 



