24 THE PLAGIOSTOMIA. 



front of the pectorals. Dorsal behind the middle of the trunk, above the space 

 between the pectorals and the ventrals. Second dorsal and anal rather large. 

 Tail compressed, without lateral folds, with a pit at the root of the caudal. 

 Caudals elongate; subcaudal followed by a shallow notch, lobe moderately 

 produced. 



Nurnerous fossil species known from the teeth have been described from 

 the Eocene and later. 



Teeth without denticles owstoni (page 24) 



Teeth with one denticle at each side 



dorsal in front of the ventrals, first upper tooth smaller than second 



rows of teeth |^ taurus (page 25) 



dorsal partly above the ventrals, first upper tooth equal second 



rows of teeth |§^ tricuspidatus (page 26) 



Teeth with two denticles at each side 



rows of teeth f| ferox (page 27) 



Carcharias owstoni, sp. nov. 



Body fusiform, robust; head depressed; snout medium, rather pointed, 

 broader than deep. Nostrils transverse, nearer to the mouth than to the end 

 of the snout, anterior valve with a short rounded prominence on its inner half. 

 Mouth large, length nearly two thirds of the width, outline broadly rounded 

 in front; lower labial fold nearly one third of the length of the jaw, upper, rudi- 

 mentary, a mere gash hidden by the lip. Teeth much smaller than those of 

 C. taurus on individuals equal in total length : in C. taurus the third tooth of the 

 lower jaw of a thirty-eight inch specimen measures a little more than half an 

 inch; in C. owstoni this tooth is a little less than three eighths of an inch. Teeth 

 lanceolate slender, two-rooted; first upper tooth little smaller than the second 

 from the middle, fourth upper very small and followed by a vacant space; first 

 lower small; bases without denticles at the sides of the cusps. Eye small, 

 diameter of orbit one third of the preoral length of the snout. Spiracle small, 

 three lengths of the orbit behind the eye, above the angle of the mouth. Gill 

 openings wide, hindmost in front of the pectorals, width equal length of snout 

 from the mouth. Front edge of pectoral broadly curved, nearly twice the length 

 of the hinder edge, inner angle much rounded. Hind margins of all fins concave. 

 Dorsal origin behind the ends of thepectorals, extremity of fin reaching a vertical 

 from the ventrals, little larger than second dorsal, ventrals or anal, which are 

 subequal and somewhat less in size than the pectorals. Ventrals below the 



