258 



BUI.LETIN OF THE BUREAU OF FISHERIES. 



denticles grade into a form which has three sharp-pointed lobes on the apical margin, with a deep 

 indentation between the lobes, keels high and distinct. These differences may be noted without the 

 aid of a microscope by passing the fingers forward over the surface of the skin, that portion devoid of 

 apical lobes feeling comparatively smooth. In the example 182.9 *^™- long, the denticles are closer 

 together, and in nearly all cases the median keel projects slightly, apical margin more rounded. The 

 characteristic form and sculpturing of the denticles in this species have proved to be of marked value 

 in identifying the species. 



Measurements of a Specimen (No. i) 81 Cm. {31H Inches) Long from Cape Lookout, N. C, 

 AND One (No. 2) 182.9 Cm. (6 Feet) Long from Woods Hole, Mass. 



Total length 



Tip of snout to — 



Origin of first dorsal 



Anterior margin of eye 



First gill slit , 



Last gill slit , 



Base of pectoral 



Front of mouth 



Outer angles of nostrils , 



Depth of body at origin of dorsal 



Horizontal diameter of orbit 



Distance between nostrils , . , 



Length of nasal aperture 



Distance between angles of mouth 



Height of— 



First gill aperture 



Second gill aperture , 



Third gill aperture 



Fourth gill aperture , 



Fifth gill aperture 



Length of anterior margin of first dorsal 



Length of posterior margin of first dorsal. . . , 



Base of first dorsal 



Distance between dorsals 



Length of anterior margin of second dorsal. . , 



Length of posterior margin of second dorsal.. 



Base of second dorsal 



Distance from second dorsal to caudal 



Length of outer margin of pectorals 



Length of inner margin of pectorals , 



Breadth of pectorals '. . , 



Ajcil of pectorals to origin of ventrals 



Length of outer margin of ventrals , 



Length of inner margin of ventrals , 



Breadth of distal margin of ventrals 



Length of claspers 



Length of anterior margin of anal 



Length of posterior margin of anal 



Base of anal 



Axil of anal to lower caudal lobe , 



Length of upper caudal lobe 



Length of subcaudal lobe 



Tip of caudal to notch in upper lobe 



Breadth of distal margin of caudal tip 



No. 



cm. 

 81.0 



24.0 



7-8 

 16.4 

 19- S 



18.7 

 6.9 

 4.8 



II. 4 

 1-7 

 4.9 

 1.4 

 7-5 



3-2 

 2.9 

 2.9 



2-7 



1.8 



2.0 



27 

 9.6 



18.7 

 4.0 

 3-4 

 3.6 



Na. 2. 



cm. 

 183.9 



S8.S 

 16.9 



38- s 



49- S 

 44.0 

 IS- 1 

 9.8 



2.8 

 IO-6 



31 

 16. 1 



5-8 

 S'9 

 5-7 

 5-S 

 4-6 

 36.1 

 9-3 



30.0 



9.6 



7-4 

 8.1 

 14- o 

 36.0 

 ll.o 

 110.4 



7- J 

 8.1 



10-9 

 43.3 

 22. 7 



Snout (in smaller example, a male) short, broad, blunt, its length slightly greater than distance 

 between angles of mouth; nostrils widely separated, distance from outer angle to tip of snout nearly 

 1.5 in preoral length, aperture less than diameter of eye, valves with a short, pointed lobe. 



First dorsal high; upper lobe rounded; posterior lobe produced, acute; distal margin concave, 

 origin over axil of pectoral; second dorsal small, acuminate behind; distal margin very slightly con- 

 cave; origin of fin in advance of anal; pectorals large, breadth 1.7 in length, distal margin slightly 

 concave; ventrals truncate, claspers small; anal slightly larger than the second dorsal, distal margin 

 deeply concave; caudal large, about one-fourth total length, subcaudal lobe large. 



The larger individual agrees in general with the one just described. The nasal aperture is greater 

 than diameter of eye, the first dorsal is more erect and the upper lobe is more pointed, distal margin 

 slightly sinuous, concave posteriorly; second dorsal considerably smaller than the anal; caudal about 

 3.7 in total length. 



