Fishes of the Western North Atlantic 59 



as the base; origin of first dorsal posterior to tips of pelvics by a distance about equal 

 to base of first dorsal or a little greater. Interspace between dorsals about twice as 

 long as base of first dorsal. Interspace between rear end of base of second dorsal and 

 upper origin of caudal about i. 0—1.2 times as long as base of second dorsal. Upper 

 origin of caudal a little anterior to lower; upper margin weakly convex, about i — 1.5 

 times as long as interspace between dorsals; lower posterior contour well rounded, 

 without distinct lower lobe; height of caudal above extremity of axis about as great 

 as its depth below latter. Caudal axis only slightly raised (perhaps horizontal in some 

 cases). Pelvics with anterior, inner and distal margins nearly straight, the outer corners 

 broadly rounded, forming an angle of about 1 30°, the posterior corners narrowly 

 rounded; extreme length of pelvics, origin to rear tip, about 1.6-1.8 times as great 

 as distance from origin of pelvic to axil; their axils separated by a distance about 

 1. 2-1. 4 times as great as breadth of mouth. 



Rostral cartilage nearly uniform in breadth throughout most of its length, widening 

 in somewhat rounded outline toward tip, its maximum breadth there about i.o— i.i 

 times as great as distance between inner ends of nostrils; its ridges close together and 

 approximated at tip. Anterior rays of pectorals extending anterior to nasal capsules of 

 cranium by a distance about 1.3— 1.4 times as great as distance between nostrils. 



Color. Upper surface uniform olive gray or chocolate brown, without pale or dark 

 markings. Lower surface either a pale shade of the same hue as upper surface or as 

 dark as upper surface;" snout with an oval sooty patch in some but only faintly washed 

 with sooty in others. *5 



Relation to Extralbnital Species. R. horkelii closely resembles R. cemiculus St.-Hilaire 

 1827 of the eastern Atlantic but appears to be separable from it by a longer snout 

 and by the facts that the outer of the two folds on the posterior margin of its spiracle 

 is conspicuously larger than the inner and that there are 3—4 tubercles on each of its 

 shoulders (only two in R. cemiculus)\ furthermore, horkelii seems to be separable from 

 cemiculus by the presence of a larger number of tubercles (about 70; see p. 49) along 

 the midline of its back from nuchal region to first dorsal fin (only about 18-20 in 

 R. cemiculus).^^ 



R. horkelii is closely allied to R. productus of the Pacific Coast of Mexico and 

 California, but when half-grown or larger it is separable from R. productus by the fact 

 that the origin of its first dorsal fin is posterior to the tips of the pelvics by a distance 

 about as great as that between the eyes or about as long as the base of the first dorsal 

 (less than half as long as distance between eyes and only a little more than half as long 

 as base of first dorsal in R. productus). The tubercles around the eyes and on the shoulders 

 are more prominent in R. horkelii than in R. productus, those in the median dorsal row 

 larger and more regularly arranged, especially in the interspace between the two dorsal 



44. Specimens with pale undersurfaces were classed as a color variety in the original account of the species. Those that 

 we have seen are paler below than above, but evidently they have lost most of their original color. 



45. Our Study Material includes examples of each of these color phases. 



46. The original illustration of R. cemiculus (St.-Hilaire, in Savigny, Zool. Egypte, i [i], 1827: pi. 27, fig. 3), modified 

 by Fowler (Bull. Amer. Mus. nat. Hist., yo [i], 1936: too, fig. 37), shows only 18. 



