7. GALEORHINID.E MUyTELUS. 19 



sixty species; found in all sea.s. {Carchariidiv part {Carcharlbia and 

 Mwstelina) Giiuther, viii, 357-380, and 383-388.) 



* Teetli Hat aiulpiived, without cusps or cuttinj^cdj^es; spiracles juesciir. {MunteUn(e.) 



a. No i)it at the i"(H)t of the tail; labial folds well devol()p('<l Mi'stkixs 14. 



**Teetli more or less eompressed, with entire or serrate shariKcdncs. {(rahorhiiiina:.) 

 b. Spiracles ])resent. 

 c. No pit at the root of the tail. 



(I. Teeth small, eaeh with a median cusp and one or two small lateral cusps 



on each side Triacis, 15. 



(Id. Teeth laricer, with a sinjjjle cusp, ol)li(|ue. notched .-md serrated, 



{iALKOUniNlJS, 1(5. 

 <T. A pit at the root of the t.ail ; teeth all serrate; caudal tin with a double 



notch - GALKocKKno. 17. 



bb. Spiracles obsolete. 



e. Teeth serrate, more or less (entire in the very young or very old) ; little 

 ol)li(jue or nearly upright. 

 /. Teeth well serrated (in the adult); those of the u]iper jaw compara- 

 tively broad or triangular; those of the lowei- narrow and claviforin. 



Cakchauixus, is. 

 f/. Teeth scarcely serrated, constricted a( base, iiarrow, claviform, and 



straight in both .jjtws Isogompiiodox, lt>. 



er. Teeth all entire. 



g. Teeth nearly upright, the points not much directed towards the 



sides AritioxoDOX, 20. 



gg. Teeth oblique and Hat, the points turned to the right or left away 

 from the centre, so that the inner margins are nearly horizontal and 

 present a cutting edge Scoliodox, 21. 



14.— MUSTELUS Cuvier, 1817. 

 {HoiDid Sharks.) 

 (Bellon, Cnvier, Regue Animal: type Mustdus ruIgarisM. & H.) 



Body elongate, slender, not elevated; snout comparatively long and 

 flattened : mouth crescent-sha])e(l, with well-developed labial folds ; 

 teeth small, many-rowed. Hat and sujooth, rhoml)i(', arranged like pave- 

 ment, alike in both .jaws; eyes large, oblong; spiracles small, just be- 

 hind the eyes; pectoral lins large ; first dorsal large, not nmch behind 

 l)e('t()rals; second dorsal somewhat smaller: anal opposite second dorsal 

 and still smaller; ventials well developed: l)asal lobe of c;iiulal almost 

 ol)Solete; embryo not attached to uterus by a i)la('eiita. Small sharks, 

 the smallest of the American s])ecies, known at oiu;e by the smooth, 

 jiaved teetli. (Latin, iiiit.stria, a weasel or iiuntin : the use of the word 

 similar to that of ya/Jr^., y/u.to-.) 



lO. in. liiiiBIUIUS (Hlainv.) .J. cV (i. — Smuolh lln-ni.l ; Diuj Sh(iil:. — VA\\\s>>o\v. 



Dody slender, tapering backward from the dorsal tin to the long 

 slender tail; snout depressed, moderately sharp ; mouth small, the teeth 

 all ahke, a fohl at the angle of the mouth ; hrst dorsal rather large, 



