Jordan and Jtvennann. Fishes of North America. 35 



.//'. Nasal Hap with an acute Inlir. 



//. Snout not very short, its length from mouth not notably lose 

 than width of mouth. Color yellowish brown. 



ACRONOTUS, 42. 



hh. Snout very short and blunt, its length from mouth but % widtli 



of mouth. PEREZI, 43. 



ee. Distance from end of base of first dorsal to ventrals greater than length 



of first dorsal ; snout moderate. REMOTVB, 44. 



././. Length of snout from mouth greater than width of mouth; first dorsal small. 



HEM LEI. 45. 



OARCHARHINUS: 

 bb. Upper teeth triangular, snberect, scarcely notched on the outer margin ; lower teeth 



similar but much narrower. 



i. Snout moderate, its length from mouth about equal to width of mouth. 

 j. Pectorals not falcate ; fins not conspicuously darker at tips. Atlantic. 



MILBERTI, 46. 



jj. Pectorals somewhat falcate ; second dorsal rather smaller than anal ; fins 

 scarcely dusky at tip. Pacific. LAMIELLA, 47. 



ti. Snout very short, its length from mouth less than width of mouth. 



k. Pectoral long and falcate, reaching to posterior part of base of dorsal. At- 

 lantic. 



I. Anterior margin of first dorsal convex, the height of the fin about equal 

 to depth of body. LAMIA, 48. 



kk. Pectoral fin moderate, scarcely falcate, not reaching to end of base of dor- 

 sal. 



m. Second dorsal not larger than anal; length of snout from mouth 1% 

 times in breadth of mouth; upper teeth very broad. Atlantic. 



PLATYODON, 49. 



mm. Second dorsal larger than anal. 



. Length of snout from mouth but ^ breadth of mouth; upper teeth 



not very broad; head very broad above. Pacific. FRONTO, 50. 



nn. Length of snout from mouth more than % breadth of mouth; 



fresh waters. NICARAGUENSIS, 51. 



ISOGOMPHODON, (10-05, equal; yd/u^os, nail; 6(W?, tooth): 



a. Teeth slightly serrated, similar in form in the two jaws, narrow, claviform, constricted at 



base; snout rather sharp. 

 o. Snout moderate, its length from mouth not greater than the breadth of mouth; teeth 



moderate, about 30 in each jaw; fins edged with black. 



p. Base of anal a little longer than that of second dorsal; pectoral reaching end of base 



of first dorsal. . JETHALORUS, 52, 



pp. Base of anal equal to that of second dorsal; pectoral reaching past base of first 



dorsal. LIMBATUS, 53. 



oo. Snout very long and narrow, its length from mouth twice distance between nostrils; 



teeth small, about 48 in each jaw. OXYRHYNCHUS, 54. 



Subgenus PLATYPODON, Gill. 

 39. CARCHARHINUS OBSCURUS, (Le Sueur). 



(DUSKY SHARK.) 



Head rather pointed, flattened above and below ; first dorsal rather 

 large ; second dorsal smaller than the anal, and considerably produced 

 behind; pectorals very large, falciform, extending beyond the end of the 

 dorsal, their outer margin 4 times the inner. Dark clear blue above, 

 white below. A large shark, reaching a length of 9 or 10 feet, inhabiting 

 the Middle Atlantic and frequently taken on our coast. (obscurus, dusky. ) 

 Squalus obscunis, LE SUEUR, Jour. Ac. Nat. Sci. Phila., 1818, 1, 223, New York. 

 Curchnrias obscuni*, GUNTHER, Cat., vin, 366,1670. 

 Gir<-h,trhitins <^.-v,o-,ix-, JORDAN & GILBERT, Synopsis, 22,1883. 

 CanJmrins falcipinnis, LOWE, Proc. Zo'31. Soc. Loud., 1839, 90, Madeira. 

 Prionodon obvehitus, VALENCIENNES, Poiss. lies Canaries, 103, 1836, Canaries. 



