1120 



SCANDINAVIAN FISHES. 



mon Skate, stands side by side with tiie most advanced 

 stages of development in the s|)ecies immediately l)re- 

 ccding it. The course followed l)y its alterations of 

 growth is sncli that, during the growth of tlie l)odv 

 from a length of 3 dm. to one of 15 dm., the length 

 of the snout increases from about 16 to 18 ?^ of that 

 of the body, in exceptional cases exceeding the latter 

 percentage, Or from "21 to 26 % (sometimes 27 %) of 

 the greatest breadth of the disk. In another of our 

 species, the so-called plogjernfirocka (Baja vomer) of 

 Fries, where the alterations of development, however, 

 are .scarcely known, these percentages for the length of 

 the snout vary between about 20 and 24 in relation to 

 the length of the body and between about 31 and 35 

 in relation to the breadtii thereof. Tlie tirst-mentioned 

 alteration during growtli of the proportion to the length 

 of the body indeed depends in great part on another, 

 which we have also observed above, namely the rela- 

 tive abbreviation of the tail with increasing age; but 

 iierewith is associated in the common Skate a difference 

 of sex, which is expressed by the comparatively greater 

 length of the abdominal region in the females than in 

 the males. This is distinctly shown by the relations 

 between the distances from the tip of the snout on the 

 one hand of the mouth or no.strils, on the other of the 

 cloacal aperture. The distances of the mouth and eyes 

 from the tip of the snout are about equal in these Kays, 

 and decrease in male specimens of the common Skate 

 from about 53 to 38 % of the distance between the 



mouth and the cloacal aperture, whereas in the females 

 these percentages diminish from about 51 to 27. The 

 Long-nosed Skate represents in this resjiect the male 

 cliaracters of the common Skate; but in the former 

 species, owing to the different prolongation of the snout, 

 which is longest in the females, the sexual distinction has 

 been reversed, the distance between the mouth and the 

 tip of the snout being in adult males about 58 — 60 % 

 of that between the former and the cloacal aperture, 

 in the females about 75 — 80 % of the same. The males 

 of the two species may consequently approximate so 

 closely to each other in form of liody that the limit 

 between the species is difficult to fix. Furthermore 

 Parnell in Scotland, Bonaparte in the Mediterranean, 

 and CoLLETT in Trondhjem Fjord have each distinguished 

 an intermediate form to fill the gap between the lines 

 of demarcation. This intermediate form has retained 

 one of the juvenile characters of the common Skate, 

 namely the aculei arming the supraorbital margin, 

 which disappear in old specimens of the common Skate, 

 and are wanting in the Long-nosed Skate. In Trondhjem 

 Fjord this intermediate form has acquired a still darker 

 (brownish black) ventral side; but even this peculiaritv 

 seems primordially to have been a sexual character, 

 the males, according to Storm, being darker than the 

 females. The more northern common Skate, with its 

 more stronglj' marked female characters, thus repre- 

 sents an original form from which the two remaining 

 species are descended. 



THE COMMON SKATE (sw. slAtrockan). 



RAJA BATIS. 



Plate XLVIII. 



Length of the snout from the anterior margin of the eyes about 14 — 18 % of the length of the body or 21 — 26 % 

 of the greatest breadth of the disk. Distance between each nostril and the tip of the snout about 21 or 22 % of 

 tlie said breadth and less than tn-ice {ISO — 140 % of) the ititcriiasal iridfh. Least iiderorbital ividth more than 

 ^/i {about 30 — 42 %) of the length of tlie snout. Aculei n-ithout grooves {or u-ith extremely faint ones). A row 

 of aculei either in the upper median Hue of the tail or on each of its lateral margins, seldom, simultaneously ' 

 present on the former and the latter. The second dorsal fin ends at a distance from the tip of the tail measuring 

 more than half its own base, and the tip of the tail is furnished above with a distinct caudal fin. Ventral side 



grayish or darker, dotted and streaked u:ith black. 



Si/n. Baja undulata sive cinerea, Rondel., De Pise, p. 346. Haja 

 Ucvis {Tepel), Schonev., Ichth. Slem. Hols., p. 58. Raja 

 laivis undulata seu cinerea Rondeletii, Willughb., Hist. 

 Pisc, p. 69, lab. C, 5. Haja varia, dorso medio glabro, unico 

 aculeorum ordine in cnuda, .Vrt., Iclith., Gen. Pisc. p. 73; 

 Syn. Pisc, p. 102. ."^kata, Raja (Umjor ct vulgaris) dorso 



non aculeato, Olafs., Peise Isl., pp. 359 et 987. Skate 

 1. Eokke, Raja clavata Auctt., Ste6m, Sondm. Beski:, p. 

 309; cfr Trondhj. Selsk. Skr., vol. I, p. 148. 

 Raja hatis, LiN., iSi/st. Nat., ed. X, tola. I, p. 231: Pemn. 

 (Skate), Brit. Zool. (cd. 177IJ), vol. Ill, p. 72, tab. IX; 

 Bl., Fisch. Deutschl, part. Ill, p. 54, tab. LXXIX; Hollb. 



