Fishes of the Western North Atlantic 243 



9b. Lower anterior corner of caudal noticeably expanded as a rounded 

 lobe from shortly after birth. 



lOa. Teeth high-crowned, their outer margins deeply concave even 

 in adults, and sometimes the inner as well. 



dorsalis Gill, 1864. 



Pacific Panama, Peru. 



lob. Teeth low-crowned, their tips bluntly rounded, their margins 

 only slightly concave in adults. 



iia. Inner margin of pectoral 60 to 63% as long as outerj 

 distance between nostrils only about 1.3 times as long as 

 upper labial furrow j dermal denticles on shoulders 

 ridged only near their bases, their tips smooth. 



mustelus Linnaeus, 1758. 

 Eastern Atlantic, Mediterra- 

 nean. 

 lib. Inner margin of pectoral only about 48 to 54% as long 

 as outer 5 distance between nostrils at least 1.3 to 1.7 

 times as long as upper labial furrow 5 denticles usually 

 strongly ridged to their tips. 



cams Mitchill, 1815, p. 244. 



Key to the Western Atlantic Species" 



I a. Head to origin of pectoral considerably longer than interspace between ist and 2nd 



dorsals. fasciatus GzTma.n, I9i3,p. 256. 



lb. Head to origin of pectoral not longer than interspace between ist and 2nd dorsals. 



2a. Lower anterior corner of caudal sharp-pointed and directed rearward (Fig. 



43 D). norrisi Springer, 1939, p. 254. 



2b. Lower anterior corner of caudal broadly rounded. 



3a. Horizontal diameter of eye only about 60% as long as 3rd gill openings 

 teeth symmetrical, evenly convex in outline (Fig. 42 J). 



mento Cope, 1877, p. 259. 

 3b. Horizontal diameter of eye about as long as 3rd gill opening; teeth some- 

 what asymmetrical, their cutting edges more or less concave. 

 4a. Lower anterior corner of caudal not appreciably expanded, even in adult 

 (Fig. 42 F) ; distance between nostrils only about '^/z as great as breadth 

 of mouth. schmitti Springer, 1939, p. 261. 



4b. Lower anterior corner of caudal noticeably expanded as a rounded lobe 

 from shortly after birth (Fig. 42); distance between nostrils consider- 

 ably more than V2 as great as breadth of mouth. 



canis Mitchill, 18 15, p. 244. 



5. This simplified Key is offered for assistance in the identification of species from the American Atlantic coast. 



