28 Bulletin 47, United States National Museum. 



CARCHARHIMNvE: 



cc. Spiracles obsolete; lower teeth narrower than upper teeth. 



g. Angle of mouth without groove or with merely a slight depression, which does 



not extend along either jaw. 



h. First dorsal fin inserted posteriorly, nearer ventrals than pectorals; emliryo 



not joined to the uterus by a placenta; slender sharks, with very strongly 



serrated teeth. PRIOXACE, 24. 



hh. First dorsal inserted anteriorly, nearer pectorals than ventrals; embr\<> (so 



far as known) attached to the uterus by a placenta. 

 . Teeth all serrate more or less, often entire in the very young. 



CARCHARHINVS, ~i^. 

 M. Teeth of upper jaw serrate at base only; lower teeth entire, erect. 



HYPOPRIOX, 2<;. 



Hi. Teeth all entire at all ages, and nearly all erect. APRIOXODOX '27. 



gg. Angle of mouth provided with a more or less distinct groove which extends along 



one or both of the jaws; teeth entire, or very nearly so, more or less obliquely 



placed, their points turned away from the median line; embryo (so far as 



known) with a placenta. SCOLIODOX, 28. 



1 8. MUSTELUS, Cuvier. 

 (Boa SHARKS.) 



Mustelus, CUVIER, Regne Animal, Ed. 1, 128, 1817, (mustelus and cam's). 



Mustelm, GILL, Proc. Ac. Nat. Sci. Phila., 1864, 148, (restricted to canis and its relatives, the 

 allies of Mustelm being called Pleuracromylon). 



Body elongate, slender ; snout comparatively long and flattened ; mouth 

 crescent-shaped, with well-developed labial folds; teeth small, many- 

 rowed, flat and smooth, rhombic, arranged like pavement, alike in both 

 jaws, and blunter than in any other sharks; eyes large, oblong; spiracles 

 small, just behind the eyes; pectoral fins large; first dorsal large, not 

 much behind pectorals ; second dorsal somewhat smaller ; anal opposite 

 second dorsal and still smaller ; ventrals well developed; basal lobe of 

 caudal almost obsolete, the tail nearly straight ; embryo not attached to 

 the uterus by a placenta. Small sharks, among the smallest of the Ameri- 

 can species, (mustelus, a weasel or marten ; the same word used for shark, 

 as is the synonymous word galeus.) . 



a. Middle of first dorsal evidently nearer posterior root of pectoral than anterior root of ven- 

 tral; snout long, its length from mouth more than width of mouth; teeth blunt. Em- 

 bryo not examined, probably as in M. canis. LUNTJLATUS, 30. 



aa. Middle of first dorsal about midway between pectorals and ventrals (as above measured). 

 First dorsal higher than long, the tip of anterior lobe reaching, when depressed, beyond 

 tip of posterior lobe, its free margin deeply incised, its base 2% times in interval between 

 dorsals; teeth blunt. CAMS, 31. 



30. MUSTELUS LUNULATUS, Jordan & Gilbert. 

 (GATO.) 



Free margin of fins concave; first dorsal high, its narrow anterior lobe 

 reaching tip of the slender posterior lobe when deflected, the fin about as 

 high as long; interval between dorsals 2f times base of first ; lower lobe 

 of caudal pointed ; tail 5 in body, its terminal lobe more than A- its length ; 

 pectoral rather sharp, its free margin incised, its tip about reaching mid- 

 dle of dorsal. Embryo unknown (probably without placenta). Very 



