Fishes of the Western North Atlantic 255 



First dorsal fin: vertical height 7.9, 8.1 5 length of base 10.4, 10.9. 



Second dorsal fin: vtT{\cz\\\&\g\\t G.iy 5.8; length of base 8.2,7.9. 



Anal fin: vertical height 3.0, 3.55 length of base 5.9, 5.4. 



Caudal fin: upper margin 1 8.4, 17.8 ; lower anterior margin 8.6, 8.2. 



Pectoral fin: outer margin 12.5, 12.65 inner margin 6.1, 5.8; distal margin 8.5, 



9.1. 



Distance from snout to: ist dorsal 28.6, 27.5; 2nd dorsal 61.2, 63.25 upper caudal 



81.6, 82.2} pectoral 17.9, 17.25 pelvics 41.9, 42.4; anal 65.2, 67.7. 



Intersface between: ist and 2nd dorsals 23.4, 25.2; 2nd dorsal and caudal 12.8, 



11.1} anal and caudal 8.3, 8.0. 



Distance from origin to origin of: pectoral and pelvics 24.4, 26. i } pelvics and anal 



23.8,25.6. 



M. norrisi resembles canis so closely that the points of difference alone need be noted. 

 These are: lower anterior corner of caudal acute instead of rounded, directed rearward, 

 forming a distinct but short lobe (Fig. 43 D)} midpoint of base of ist dorsal nearer to 

 origin of pelvics than to axil of pectoral by a distance about equal to horizontal diameter 

 of eye, instead of as near to axil of pectoral as to origin of pelvics, or nearer} body cavity 

 relatively shorter, with origin of pelvics about midway between origins of pectorals and of 

 anal, and under rear tip of ist dorsal, instead of being considerably nearer to origin of anal 

 than to origin of pectorals and behind rear tip of ist dorsal} pectorals with relatively shorter 

 inner and distal margins, the latter more deeply concave} mouth narrower} fins generally 

 smaller} labial folds not only shorter but the upper and lower folds of more nearly equal 

 length than is usual in typical canis, in which the upper is in most cases considerably the 

 longer} space between nostrils relatively narrower} trunk more slender, with its dorsal 

 outline less highly arched. The teeth also are higher-crowned in general, their margins 

 more deeply concave or even notched (Fig. 43 F)} dermal denticles, however, not dis- 

 tinguishable from those of typical canis. 



Color. No information is available as to its color in life} preserved specimens are gray 

 above, paler gray or dirty white below and without definite markings. 



Size. Norrisi reaches a corresponding stage in development at a size somewhat smaller 

 than does canis, the subocular fold being continuous anteriorly with the edge of the upper 

 eyelid, and the claspers of large size in males as small as about 620 mm. in length. And 

 females also may mature at a size no greater than this, one of 825 mm, having been found 

 to contain embryos nearly ready for birth. 



Develofmental Stages. It is not yet known whether or not the embryo develops a 

 placental connection with the mother, as in canis and in mustelus (p. 247). 



Habits. Nothing is known of its diet or of its breeding habits. 



Range. This Dogfish is known up to the present time only from the Florida Keys 

 and from the west coast of southern Florida (Englewood and Naples, where large num- 

 bers have been taken in mackerel nets). It has been taken only in winter, suggesting that 



