26 THE PLAGIOSTOMIA. 



orbit about one third of the preoral length, or of the distance from the spiracle, 

 or two fifths of the distance from the nostrils, front edge behind the front of the 

 lower jaws half the length of the orbit. Spiracle small, behind the eyes above 

 the angle of the mouth. Gill openings wide, in front of the pectorals, width of 

 hindmost four fifths of the length of the snout. Pectorals subtriangular, front 

 margins slightly convex. Dorsals, ventrals and anal about equal in size. 

 Origin of first dorsal above the extremity of the pectoral, base equal the height 

 or three fourths of the distance from the second dorsal, end of fin reaching a 

 vertical from the ventrals, hind margin slightly concave. Ventrals below the 

 space between the dorsals, ends reaching little behind the origin of the second 

 dorsal. Second dorsal as large as first, base equal distance from the caudal. 

 Origin of anal, below middle of second dorsal base, length of base nearly twice its 

 distance from the caudal. Depth of caudal less than half the length, which 

 latter is less than one third of the total length; subcaudal lobe produced, rounded 

 on the extremity. Caudal peduncle strong, compressed, with a pit at the root 

 of the caudal, without lateral keels. 



Total length 38, snout to abdominal pores 20, snout to dorsal 15, snout to 

 fifth gill opening 85, snout to mouth 2, and length of caudal ll| inches. 



Ashy gray, lighter below, spotted and blotched with rusty brown. 



Specimen described and figured from Buzzard's Bay, Massachusetts. 



Atlantic and Mediterranean. 



Carcharias tricuspidatus. 



Odonlaspis americanus Gunther, 1870, Cat. fishes Brit, mus., 8, p. 392 (part i. 

 Carcharias tricuspidatus Day, 1878, Ind. fishes, p. 713, pi. 186, f . 1. 

 Odontaspis tricuspidatus Day, 1888, Ind. fishes, Suppl., p. 810. 



This species is accepted on the authority of Day and Gunther. It is evident 

 from the description by the latter of his species Odontaspis americanus that it 

 pertains to a distinct form, in which the first tooth of the upper jaw is not 

 smaller than the second and in which the first dorsal is very close to the ventrals. 

 Additional items from Day give his C. tricuspidatus a rather broadly rounded 

 snout, place the origins of the ventrals below the hindmost third of the base of 

 the first dorsal and the origin of the anal below the end of the first fourth of the 

 second dorsal, make dorsals, ventrals, and anal about equal in size, give the 

 pectoral a very sharp outer angle, locate the gill openings entirely above the 

 level of the pectorals, put the eyes near one length of the orbit behind the for- 

 ward ends of the lower jaws, and make the number of rows of teeth 30Z34. As 



