384 Memoir Sears Foundation for Marine Research 



Distinctive Characters. Among ridge-backed members of the genus, obscurus has 

 frequently been confused with milberti. But It is easily separable from the latter by the 

 following characters: the first dorsal is somewhat less in vertical height than the distance 

 from the eye to the first gill opening and it originates over or a little posterior to the inner 

 corner of the pectoral (much larger and originating over the axil in milberti) ; the free 

 rear corner of its second dorsal is about 1.5 times as long as the vertical height (only about 

 as long as the vertical height in milberti) ; its dermal denticles are regularly overlapping 

 and with toothed margins. It is easily separable from the other ridge-backed species jalcp- 

 formis and floridanus by the shape of the second dorsal and anal fins (see Key, p. 323) j 

 from longim.inus by the shape of the first dorsal and by the remoteness of the tip of its 

 anal from the caudal. 



It most closely resembles the newly described springeri, Bigelow and Schroeder, 1944 

 (p. 404), but differs from it in a number of respects, most noticeably: (a) in a consider- 

 ably smaller eye relative to the lengths of the gill openings; (b) that the anterior margin 

 of its nostril is not definitely lobed; (c) the distance from the tips of its pelvics to the origin 

 of its anal is relatively longer (about 1.3 times as long as the base of the anal in obscurus, 

 but only about 0.7 that long in springeri) ; (d) the outer corner of its pelvic is considerably 

 more obtuse than a right angle, or about 115° (only about a right angle in springeri) ; and 

 (e) its denticles usually have fewer teeth than those of springeri at corresponding stages 

 in growth. The teeth of the two species also differ somewhat in detail (cf. Fig. 71 C-G 

 with78E-I). 



Description. Proportional dimensions in per cent of total length. Male, 993 mm., 

 from Buzzards Bay, Mass. (Harv. Mus. Comp. ZooL, No. 35371). Female, 996 mm., 

 same locality (Harv. Mus. Comp. ZooL, No. 35312). 



Trunk at origin of pectoral: hrea.dth. 11.9, 13.7; height 13.3, 12.9. 



Snout length in front of: outer nostrils 3.5, 4.O; mouth 7.9, 7.9. 



Eye: horizontal diameter 1.9, 1.7. 



Mouth: breadth 7.9, 9.2; height 4.7, 4.9. 



Nostrils: distance between inner ends 6.2, 6.3. 



Gill opening lengths: ist 2.6, 2.93 2nd 2.8, 3.4; 3rd 3.2, 3.5; 4th 3.2, 3.5; 5th 



2.7,2.9. 



First dorsal fin: vertical height 7.6, 8.6; length of base 9.8, 9.6. 



Second dorsal fin: vertical height 2.3, 2.6; length of base 4.0, 3.5. 



Anal fin: vertical height 3.1, 3.4; length of base 3.9, 4.5. 



Caw^a/^w.-upper margin 27.4, 28.8; lower anterior margin 11. 2, 11.4. 



Pectoral fin: outer margin 17.4, 18.5; inner margin 5.0, 5.2; distal margin 13.O, 



14.I. 



Distance from snout to: 1st dorsal 30.7, 32.O; 2nd dorsal 62.2, 61. 2; upper caudal 



72.6, 71.2; pectoral 22.6, 23.7; pelvics 50.2, 48.5; anal 62.6, 61.2. 



Interspace between: ist and 2nd dorsal 22.7, 21.2; 2nd dorsal and caudal 6.4, 6.1 ; 



anal and caudal 6.1, 5.9. 



