ALOPIID^. — VIII. 17 



10. CARCHARHINUS Blainville. (C ar char ias Cuvier.) 



(Kiipxapos, rough ; pim], shark.) 

 (The largest genus of sharks, represented in most warm seas. 

 It is often divided into several genera, but intergradations make 

 it difficult to maintain these divisions. In young specimens the 

 serration of the teeth is not evident.) 



a. First dorsal far behind pectoral, nearer root of ventral than that of pec- 

 toral. ( Carckarh inus.) 



13. C. glaucus (L.). Great Blue Shark. Snout very long; 

 color grayish blue. A large shark, rare on our coast. (Eu.) 

 (Lat., grayish blue.) 



aa. First dorsal not far behind pectoral. 



b. Upper teeth oblique; deeply notched on outer margin. {Platypodon 

 Gill.) 



14. C. obscurus (Le Sueur). Pectorals large; second dorsal 

 evidently smaller than anal ; first dorsal large ; head pointed. 

 L. 10 feet. N. Atl. Frequently on our coast. 



bb. Upper teeth sub-erect, triangular, scarcely notched at outer margin. 

 {Eulamia Gill.) 



15. C. caudatus (Dekay). Snout moderate, its length from 

 mouth forward not less than width of mouth ; pectoral fin not very 

 long. Atlantic coast : a httle known species of uncertain synon- 

 ymy. (Lat., long-tailed.) 



11. SCOLIODON Muller & Henle. 

 (o-(foX toy, oblique; oScoi/, tooth.) 



16. S. terrae-novae (Richardson). Sharp-Nosed Shark. 

 Body slender ; snout depressed ; mouth with short labial grooves 

 on both jaws; second dorsal smaller than anal; gray, tail dusky- 

 edged. West Indies, N. to Cape Cod, common S. (erroneously 

 ascribed to Newfoundland). (Lat. terra, land ; nova, new. New- 

 foundland.) 



Family VIIT. ALOPIID^. (The Thresher Sharks.) 



Body rather slender ; snout short ; teeth equal, flat, triangular, 

 entire; gill openings moderate, the last above P.; no nictitating 

 membrane ; spiracles obsolete ; first dorsal large, second dorsal and 

 anal very small ; tail about as long as rest of body ; no caudal keel ; 

 pectorals falcate, very large. One species, a large shark, found in 

 most warm seas. 



12. ALOPIAS Rafinesque. (dXcoTr?;^, a fox.) 



17. A. vulpes (Gmelin). Thresher. Swingle-Tail. Fox 

 Shark. Color gray. L. about 20 feet. Open sea; occasionally 

 on our coast. (Eu.) 



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