1120 
SCANDINAVIAN FISHES. 
mon Skate, stands side by side with the most advanced 
stages of development in the species immediately pre- 
ceding it. The course followed by its alterations of 
growth is such that, during the growth of the body 
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 plogjernsrocka ( 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 breadth thereof. The first-mentioned 
alteration during growth 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 
herewith 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 nostrils, on the other of the 
cloacal aperture. The distances of the mouth and ej’es 
from the tip of the snout are about equal in these Rays, 
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 respect the male 
characters 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 body 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 peculiarity 
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 strongly marked female characters, thus repre- 
sents an original form from which the two remaining 
species are descended. 
THE COMMON SKATE (sw. slatrockam). 
RAJA BATIS. 
Plate XLVI1I. 
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 betiveen each nostril and the tip of the snout about 21 or 22 % of 
the said breadth and less than twice ( 180 — 140 % of) the internasal width. Least interorbital width more than 
V 4 ( about 30 — 42 %) of the length of the snout. Aculei without grooves {or with extremely faint ones). A row 
of aculei either in the upper median line 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 oivn base , and the tip of the tail is furnished above with a distinct caudal fin. Ventral side 
grayish or darker , dotted and streaked with black. 
Syn. Raja undulata sive cinerea , Rondel., De Pise., p. 346. Raja 
Icevis (Tepel), Schonev., Ichth. Slesv. IIols., p. 58. Raja 
Icevis undulata seu cinerea Rondeletii, Willtjghb., Hist. 
Pise., p. 69, tab. C, 5. Raja varia, dorso medio glabro, unico 
aculeorum ordine in cauda, Art., Ichtli., Gen. Pise., p. 73; 
Syn. Pise., p. 102. Skat a,, Raja (major et vulgaris) dorso 
non aculeato, Olafs., Reise Isl., pp. 359 et 987. Skate 
1. Roklce, Raja clavata Auctt., Strom, Sondm. Beskr., p. 
309; efr Trondhj. Selsk. Skr., vol. I, p. 148. 
Raja batis, Lin., Syst. Nat., ed. X, tom. I, p. 231; Penn. 
(Skate), Brit. Zool. (ed. 1776), vol. Ill, p. 72, tab. IX; 
Rl., Fiscli. Deutschl., part. Ill, p. 54, tab. LXXIX; Hollb. 
