466 



PROCEEDIIS'GS OF THE NATIONAL. MUSEUM 



VOL. 86 



to the posterior apex. Color uniform gray, without Hght or dark 

 spots or bands. 



Comparisons with other species. — Mustelus schmitti is most closely 

 allied to M. canis. The most striking difference is in the smaller 

 size of the eye, but this character is less reliable in old specimens in 

 which the proportionate size of the head is reduced. The distance 

 between the nostrils is less than the horizontal diameter of the orbit 

 in all the specimens of M. schmitti examined, whereas in the large series 

 of M. canis examined the internasal distance was always as great as 

 and usually greater than the horizontal diameter of the orbit. The 

 dermal denticles are less uniform in structure than in AI. canis, the 

 ridges of the denticles of the lateral surfaces extend only about two- 

 thirds the distance to the posterior apex. A few denticles with five 



Table 1. — Measurements (in millimeters) of the types of Mustelus 



Measurement 



Total length... 



Tip of snout to- 

 anterior margin of the orbit. 



front of mouth (length snout) 



outer angle of nostril 



first gill opening 



last gill opening 



base of pectoral 



anus 



Horizontal diameter of orbit 



Vertical diameter of orbit... 



Mouth, angle to angle (width mouth) 



Internasal 



Length mouth 



Length, outer labial fold 



Length, inner labial fold 



Outer margin clasper 



Inner margin clasper 



Snout to origin first dorsal 



Anterior margin first dorsal 



Posterior margin first dorsal 



Distal margin first dorsal 



Base first dorsal 



Interdorsal 



Anterior margin second dorsal 



Posterior margin second dorsal 



Distal margin second dorsal 



Base second dorsal 



Second dorsal to beginning of caudal.. 



Length upper caudal lobe , 



Length lower caudal lobe 



Tip caudal to notch 



Outer margin pectoral. 



Inner margin pectoral 



Distal margin pectoral. 



Base pectoral 



Anterior margin anal 



Posterior margin anal , 



Base anal , 



A/, schmitti 



U.S.N.M. 

 no. 106640 



55 

 45 

 37 

 123 

 156 

 152 

 332 

 17 

 8 



36 

 16 

 24 

 16 

 9 



60 

 104 

 225 

 88 

 29 

 83 

 88 

 161 

 78 

 24 

 60 

 66 

 80 

 141 

 59 

 64 

 102 

 60 

 86 

 36 

 40 

 20 

 40 



M. norrisi 



U.S.N.M. 

 no. 106639 



51 

 42 

 32 



ni 



140 



134 



317 

 20 

 10 

 36 

 19 

 24 

 8 

 7 



55 

 81 



215 

 87 

 23 

 70 

 71 



190 

 63 

 23 

 55 

 55 

 80 



133 

 58 

 45 



101 

 45 

 80 

 27 

 46 

 14 

 41 



U.S.N.M. 

 no. 57369 



57 

 44 



33 

 125 

 149 

 136 

 345 

 23 

 9 



40 

 20 

 27 

 10 

 9 



262 

 106 



24 



90 

 175 

 85 

 17 



70 

 90 



150 

 72 

 55 



125 

 55 



