W. G. STEVENSON. 87 



One row of teeth only is fully visible in either jaw, 

 though a second row is partially exposed as it rises 

 above the enclosing tissues, while four rows in the 

 upper and five rows in the lower jaw, overlying each 

 other — the teeth in each succeeding inferior row being 

 smaller and less dense — are entirely concealed in the 

 deep groove of the mucous membrane of the jaws. 

 These concealed rows of rudimentary or non-functional 

 teeth, when exposed by cutting away the enclosing tis- 

 sues, reveal, even in the smallest and most rudimentary 

 stage, the same triangular form, with serrated margins, 

 as is seen in the fully developed teeth. 



FINS. 



The pectoral fins, twenty-four inches in length, are 

 large, low, falcate, with anterior margin entire, convex. 

 The posterior margin is twenty inches long, with a large 

 lobe at the base. The pectorals are thirty inches from 

 the end of the snout (straight horizontal line), and have 

 a basal insertion of eight inches, with an antero-pos- 

 terior diameter, across the basal lobe, of thirteen inches. 



The first dorsal fin is forty-four inches behind the 

 snout, and six inches behind the pectorals. It is large, 

 triangular, ten inches high, with a basal insertion of 

 twelve inches. Its anterior margin is entire, convex ; 

 its posterior margin is somewhat repand, with a trian- 

 gular lobe at the base. 



The second dorsal fin, twenty-six and one-half inches 

 behind the first dorsal, and fourteen inches in front of 

 the caudal, is a small, somewhat rhomboidal-shaped fin, 

 only two inches high, with an obliquely truncated end, 

 and one and one-half inches wide at base. 



The ventral fins, twenty-nine and one-half inches 

 behind the pectorals, are abdominal, horizontal, fan- 

 shaped, and of medium size. No claspers. 



