242 Memoir Sears Foundation for Marine Research 



Comparative Zoology; also two eggs with embryos, one of them still with small yolk 

 sac, the other about ready to have hatched. 



Distinctive Characters. Among the Skates of the geographic province where R. ocel- 

 lata occurs, the ocellar spots usually present on the upper surface of its disc (p. 246) 

 are a reliable means of identification for specimens that have them. However, specimens 

 that lack these spots resemble R. erinacea so closely when small that the only certain 

 means of distinguishing one from the other is by the number of series of teeth, R. ocellata 

 having at least 80'* series in the upper jaw (usually 90-100), R. erinacea never more 

 than 66 (usually less than 54). Adults of the two species can also be separated by size, 

 R. ocellata not maturing until it reaches a length of at least 25-26 inches whereas R. eri- 

 nacea matures at 18-20 inches, its maximum length being only about 21 inches. What 

 is said on p. 178 as to the differences between R. erinacea and R. fyllae applies equally 

 to R. ocellata. 



R. ocellata., like R. erinacea, falls closest to R. naevus Muller and Henle 1 84 1 among 

 European Skates in shape of disc, relative length of tail, distribution of thorns, loss of 

 the mid-dorsal row of thorns with growth, and the frequent presence of a large ocellar 

 spot on the upper inner part of each pectoral. But the disc and anterior part of the tail 

 are thornier in R. ocellata., especially on females, and the skin of its disc is smooth be- 

 tween the thorns, whereas on R. naevus it is generally prickly between the thorns. R. ocel- 

 lata does not bear a close resemblance to any Skate described from the South Atlantic 

 or from the Pacific Coast of North, Central, or South America. 



Description. Proportional dimensions in per cent of total length. Female, 806 mm 

 (Harv. Mus. Comp. Zool., No. 359). Male, 809 mm, (Harv. Mus. Comp. Zool.,No. 

 352) from Massachusetts. 



Disc: extreme breadth 60.6, 64.8; length 46.6, 49.3. 



Snout length: in front of orbits i 1.6, 10.6; in front of mouth i 1.5, i i.i. 



Orbits: horizontal diameter 3.5, 4.1 ; distance between 5.3, 5.9. 



Spiracles: length 3.6, 3.5; distance between 7.8, 8.0. 



Mouth: breadth 9.9, lo.i. 



Nostrils: distance between inner ends 7.6, 6.9. 



Gill openings : lengths, ist 2.0, 2.0; 3rd 2.3, 2.3; 5th 1.7, 1.7; distance between 

 inner ends, ist 16.0, 17.4; 5th 8.8, 8.4. 



First dorsal fin: vertical height 3.2, 3.3; length of base 7.6, 7.5. 



Second dorsal fin: vertical height 3.0, 2.6; length of base 6.7, 6.7. 



Pe/wVj; anterior margin 11.7, 14.8. 



Distance: from tip of snout to center of cloaca 50.6, 49.2 ; from center of cloaca 

 to 1st dorsal 33.7, 34-7; to tip of tail 49.4, 50.8; from rear end of 2nd 

 dorsal base to tip of caudal 1.5, 1.9. 



Interspace between: ist and 2nd dorsals 0.0, 0.0. 



74. Bigelow and Schroeder (Bull. U. S. Bur. Fish., 48, 1936: 324) give as few as 70, but re-examination of the specimens 

 on which this count was based showed that the number should have been stated as 80. 



