ADDENDA 7~. CARCIIARIIDyE CARCH ARIAS. 967 



very short, its base straight, slightly oblique. Size much less than 

 that of Mola rotunda. Pelagic; occasional off our Atlantic coast. 



(Tetrodon truncalus Retz. Vet. Ak. Nya Handl. vi, 2, 116: Orihagorlscus oblo-nyus 

 Bloch & Schn. 1801, 511: Ortliagoriscus truncatus Gunther, viii, 319.) 



Page G: 



FAMILY BDELLOSTOMATID^E. 



The genera Heptatrema and Polistotrema may be recognized as con- 

 stituting a family (Bdellostomidce Gill) distinct from Myxlnldce. 



Page 12. We are indebted to Professor Gill for the following outline 

 of a proposed subdivision of the Squall. 



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

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

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



I. OPISTHARTHRI OR CYCLOSPONDYLI. 



Squall with the palato-quadrate apparatus articulated or connected with the post- 

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

 number (0 or 7) ; only one dorsal fin. The Notldanidce alone exhibit these peculiarities 

 in the existing fauna. 



II. PROARTHRI OR ACRODONTA. 



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

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

 The Heterodontldce are the only living representatives. 



III. ANARTHRI OR GALEI. 



Squall with the palato-quadrate apparatus not articulated with the skull; the den- 

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

 except the Sqitatlnidce, Heterodouiidce, and Notldanidce belong to this suborder. 



IV. RHIN^E. 



Squall with the palato-quadrate apparatus not articulated with the skull; the den- 

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

 larged anterior basal lobes which are separated by notch-like spaces from the branchial 

 region. The family of Sqiiatinidce is the only existing family of this suborder. 



Page 22, etc. The following brief "key" will perhaps facilitate the 

 identification of the species of Carcliarias, which are at present known 

 from our Atlantic coast: 



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



aa. First dorsal close behind pectoral. 



6. Upper teeth oblique, deeply notched on outer margin. (Platypodon Gill.) 



OBSCURUS.. 

 Hb. Upper teeth triangular, suberect, scarcely notched on outer margin. (Eulatnia 



Gill.) 

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



C'CERULEUS. 



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



