198 Memoir Sears Foundation for Marine Research 



each pectoral on some females but not on males. The skin of the disc and tail is also 

 rough with small prickles on small specimens, but extensive areas on the median and 

 posterior parts of the disc and on the upper surface of the tail are largely smooth in 

 adults, apart from the thorns. The pelvics are naked except for prickly patches on the 

 central parts of the posterior lobes, the dorsals are sparsely prickly. Alar spines of 

 mature males in two to three rows. Lower surface naked in adults of both sexes, but 

 described as prickly along margins of tail in newly hatched specimens.* 



Snout anterior to orbits about 2.4 times as long as distance between orbits, its 

 length in front of mouth about 2.0 times as great as distance between exposed nostrils. 

 Diameter of orbit about 1.3 times as long as spiracle, distance between orbits about 

 as great as length of orbit or a little less. Distance between first gill openings about 

 2.4 times as long as distance between exposed nostrils, distance between fifth gill open- 

 ings 1.3 times; first gill openings slightly longer than fifth and about V4 the breadth 

 of mouth. Nasal curtain deeply fringed with simple, bifid, or trifid lobelets; expanded 

 outer (posterior) margin of nostrils also fringed. Mouth moderately arched centrally, 

 the outer ends more or less concealed when closed. 



Teeth in 30—38 series, closely crowded in quincunx; those of young, and of 

 females to maturity with a circular base and low, blunt, conical cusp; those of adult 

 males with sharp cusp. 



First and second dorsal fins confluent, the second a little the larger (in specimen 

 examined) and continuous with caudal membrane, the latter about half as long as second 

 dorsal. Pelvics moderately concave, the marginal excavation having one rather notice- 

 able subtriangular projection; anterior margin about 55—60 "/o ^s long as distance from 

 its own origin to rear tip of pelvic; posterior lobe strongly convex outwardly and weakly 

 scalloped; rear tips broadly rounded. Claspers of maturing males extending about half 

 of distance from axil of pelvics toward first dorsal. 



Anterior rays of pectorals reaching about 80 "/o of distance from level of fronts 

 of orbits toward tip of snout. 



Color. Upper surface ash gray to chocolate brown, either uniform or somewhat 

 clouded with paler and darker. Young with more or less pronounced darker brown spots, 

 pale-ringed in var. Upacantha (see discussion below). Lower surface white, grayish 

 white, pale gray or light fawn color, uniform or with sooty patches on pelvics and on 

 axils of pectorals in roughly symmetrical pattern. 



Remarks. A separate varietal name, Upacantha, has been proposed* for represen- 

 tatives of R.fyllae from the Skagerrak, where, according to descriptions, the young 

 specimens are more finely prickly than those of the typical form; adults have a sparser 

 development of thorns along the midbelt of the back, and the anterior margin is defin- 

 itely notched in the adult male.'' R. fyllae of the western Atlantic are the typical 

 form, and it is these that come within the scope of the present account. 



5. Clark, J. Mar. biol. Ass. U.K., 12, 1922: 626. 



6. By Jensen, Vidensk. Medd. naturh. Foren. Kbh., 1905: 233. 



7. Clark, Rep. Fish. Bd. Scot. (1926), j, 1926: cf. pi. 24, fig. a with pi. 22, fig. a. 



