DISCUSSION OF SPECIES AND THEIR DISTRIBUTION. 25 



vided with two-rayed dorsals; skin more or less spinous; dentition differing in the two 

 sexes; the niah' usually provided with a differentiated patch of sjjines on eaeh pectoral. 



The genu.s Eniii is almost cosmopolitan, but most abundant in northern seas. 



In this genus are included the forms usually known by the name of Skate. About forty 

 species have been provisionally described, of which i)erha]ts twelve are found in the Atlantic 

 basin below the lOO-fathom line. The genus has not yet been collected at a depth greater 

 than Oil' fathoms. Of the seven species of Rata occurring on the British coast, lour at least 

 have been found in deep water. Of the nine species of the Atlantic coast of North America, 

 live have been found in the depths. 



Tlie Rays are believed to have been abundant in the Cretaceous and Tertiary periods, 

 but the species most characteristic of early geological times is allied rather to the forms 

 now living in shallow water than to those of greater depths. 



The Kays of the eastern and western Athmtic liave not been compared with a suffi- 

 ciently large number of individuals at hand, and it is probable that when this shall V)e done 

 the number of species for the north Atlantic will be considerably reduced. 



The curious egg cases of the Rays, rectangular, black, leathery, with tubular flexible 

 tendrils at each of the four angles, popularly known as '' devil's knitting sheaths " or " mer- 

 maid's purses," are well known to every stroller along tlie seashore. The large egg cases 

 of Rata hvris are especially familiar. 



An unfamiliar form of egg, large, square, and with short tendrils, was f(mnd at various 

 depths off Newport in 1880, and young skates with extremely long tails were taken from 

 them. These have not yet been satisfactorily identified, but it will possibly be found that 

 they belong to Raia ratUatu. 



RAIA RADIATA, Donovan. (Figure 27.) 



Raja radiata, Donovan, Hist. I?rit. Fish., v, pi. 114, 1820.— Stouku, Kept. Fish. Mass., 201, 1839.— MulleR 

 and Henle, Plagiostomon, 137, 1811.— Dumkril, Elasmobrauch., Tom. i, Pt. ii, 531, 1870.— Gunther, 

 Cat. Fish. Brit. Mus., viii, 460, 1870.— ChalliMiger Report, xxii, 8.— Garman, Proc. Best. Soc. Nat. Hist., 

 xvii, 1874, 178.— Goode and liEAX, Bull. F.ssex Inst., xi, 28.— Jordan, Bull, xvi, XL S. Nat. Mus., 41. 



Raja amerivana, DeKay, Zool. N. Y., Fishes, 368, pi. 66, fig. 215, 1842.— Storer, Syn. Fish. North Amer., 260, 

 1846. 



Raja la'vis. Storer, Hist. Fish. Mass., 266 (description), 1867. 



Rttid with large spinous plates or bucklers, in addition to the spines on pectorals, head, 

 back, and tail found in R. ocellata. These are large, strong spines, with broad stellate or 

 shield-like bases. They are arranged as follows : One or two in front of each eye ; one on 

 each side between the eye and the spiracle; a pair on the shoulder, the smaller in front; 

 and fourteen or more forming a dorsal row, beginning just back of the head and extending 

 to the caudal. An irregular row of spines on each side of the tail, separated from the 

 membrane by a band of shagreen; males with two or more rows of claw-like spines on the 

 pectorals. Teeth with a long, sharp point, rising from the middle and hooking backwards 

 in the male, bluntish in the female; females larger than the males and more spinous. 

 [Garman.) 



Raia radiata, which is not very uncommon at moderate depths off the New England 

 coast, but has not yet been found below the lOO-tathom line in the western Atlantic, has 

 been recorded by (Jollett from the region between Spitzbergen and Bear Island at a depth 

 of 127 to 259 fathoms, and also by Strom and CoUett, in Throndhjem Fjord in 250 fathom.' 



s. 



RAIA ACKLEYI, Garman. (Figure 23.) 



Raja AckleyijCi ARMAS, Bull. ilns. Conip. /oi'd., viii, 1881, 235. 



"Disk, including the ventrals, rhombic, longer than wide; anterior margins sinuous; 

 po.steri(u- outline convex; tail moderate, depressed, with a narrow cutaneous fold on each 

 side, tapering. The angle formed by the snout is less than right. Rostral cartilage rather 

 slender. Mouth moderate, much curved; width one and two-thirds times in distance from 



