PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 109 



posterior lobe extending farther than the anterior when depressed, its 

 distance from base of caudal more than the leugtli of its base. 



Lower lobe of caudal short l)ut pointed ; tail forming a little more 

 than one fifth the total length, its length about equal to distance from 

 snout to front of pectorals. Terminal lobe about two-fifths length of 

 tail. 



Anal much smaller than second dorsal, its posterior margin a little 

 behind posterior margin of the latter. Ventral moderate, its distal mar- 

 gin concave, the angles sharp. Pectorals comparatively sharp, half 

 longer than broad, three fourths to four-fifths length of head (to first gill- 

 slit), their length 7 to 7^ in total. 



Color very light gray above, pale below; fins all pale. 



Two half-grown specimens about 20 inches long, both numbered 29,211, 

 were obtained at Mazatlan, where it is known to the fishermen as " Gato." 



The following analysis of Americau species of Mustelus shows the relation of M. Jiuiii- 



latiis to the other species of this j^eniis : 



a. Middle of lirst dorsal evidently nearer root of pectoral (posteriorly) than root of 

 ventral (anteriorly); snout long, its length from mouth more than width of 

 mouth; teeth bluntish; free margins of fins concave; first dorsal high, its 

 narrow anterior lobe reaching tip of the slender i)osterior lobe when retiexed; 

 the fin about as high as long. Interval between dorsals 2f times base of first ; 

 lower lobe of caudal ]»ointed; tail 5 in body, its terminal lobe more than one- 

 third its length ; pectorals rather sharp, their free margin incised, their tips 

 about reaching middle of dorsal ; embryo unknown (probably without pla- 

 centa); color pale Lunulatus. 



aa. Middle of first dorsal about midway between pectorals and ventrals ; snout shorter, 

 its length from mouth about equal to width of mouth. 

 b. First dorsal higher than long, the tip of anterior lobe usually reaching, when 

 depressed, beyond tip of posterior lobe, its free margin deeply incised, its base 

 2f times in interval between dorsals; teeth bluntish; lower lobe of caudal 

 blunt ; tail more than one-fifth body, its terminal lobe more than one-third 

 its length ; pectorals rather obtuse, their free margin little incised, their tips 

 reaching first third of dorsal; inner lobe of ventrals produced; embryo not 



attached to uterus by a placenta ; colors rather pale Canis. * 



bb. First dorsal longer than high, its tip not reaching tip of posterior lobe, its free 

 margin scarcely incised, its base about half the interval between dorsals; 

 teeth rather sharp (in adults ?) ; lower lobe of caudal not acute ; tail less than 

 one-fifth total length, its terminal lobe li?ss than one-third its length ; pecto- 

 rals obtuse, their free edges almost straight, their tips reaching first fourth of 

 dorsal ; inner lobe of ventrals not produced, the free edge of the fin straight; 

 embryo unknown (pi'obably with placenta); color rather dark, axils of pec- 

 torals and ventrals duskv DonsALis.f 



* Sqxahts canis Mitchill, Trans. Lit. and Phil. Soc. N. Y. i, 1815, 486 : = Miistelns asftrins 

 Cloquet, Diet. Sci. Nat. xiv, 407, 1820:^ Sqiiahis MiniiiJus Blainv. Faune Frangaise, 

 18-20-':W, 8^ : = MnsieJus ridgaris Mliller & Henle, Plagiost. 1839, 64, and of many authors. 

 Cape Cod to Cuba ond on all coasts of Southern Europe. We are thus far unable to 

 detect any permanent diiference between European and American siieciuieus. The 

 American name has clear priority. 



f Mustelus dorsalis Gill, Proc. Ac. Nat. Sci. Phila. 1864, 149. Panama (Gill ; Gilbert). 



