344 PLAGIOSTOMATA. 



very similar to those in the females. In the males, about 40 rows of teeth in either 

 jaw, they are of two forms, the outer ones being lozenge-shaped, whereas the middle 

 ones are conical with the points turned inwards, and the rows not being quite so 

 close together. In the females the teeth are flat and in oblique rows, appearing 

 much like the heads of large nails, those in the centre being larger than the lateral 

 ones. Fins the two dorsals of about the same size, the length of the base of each 

 equalling about that from the front end of the orbit to the hind edge of the 

 spiracle : they are separated by a short space where there are generally one or two 

 spines. Usually a small caudal fin. Skin more or less covered with spiny tubercles 

 and asperities, which are very numerous on the snout and along the anterior 

 border of the wings. One or two large claw-like spines on the snout, one or 

 two at the anterior angle of the orbit, also at its posterior angle, and above the 

 spiracle. A strong median row passes from behind the head along the centre 

 of the back and tail, also a strong shoulder spine. Opposite the end of the 

 insertion of the anal fin, a lateral row commences along the side of the tail, and 

 is generally of smaller dimensions than that along the back of the tail. In the 

 males a patch of strong spines on the wings. All the spines are liable to 

 modification, while in the young the body, except the median line of the back 

 and the snout, may be nearly smooth or covered with asperities : for the spines 

 both increase in size and number with age. Those on the tail are also variable, 

 and specimens are seen with one, three or five rows, rarely without any : the 

 males generally have three rows. Colours variable, the upper surface brownish 

 and marbled all over : the under surface being white. In the young there may 

 be round brown or white spots or blotches. On each wing is sometimes seen a 

 large white spot, externally margined with black. 



Varieties. Parnell observes that he had met with three full-grow 7 n examples 

 of males in which the teeth were as blunt as those of the females. The anterior 

 portion of the pectoral fins may be abnormally detached from the head as 

 shown in figure 2. Cuvier's Ray, Baia Cuvieri, Lacepede, was 12 inches broad, 

 and the same length excluding the tail, taken in Firth of Forth, 1808, distin- 

 guished by the position of its dorsal fin w T hich is upright, of an oval shape 

 and placed in the middle of the back. M. Gervais has evidently a similar form 

 in view, when he remarks upon a case of notomely in this species, the example 

 had a pair of rudimental pectoral fins on its back (Compt. Rend. 1864, iii, p. 802). 

 In fact, these monstrosities are not very rare. Montagu observes as for the 

 tubercular spines with which both sexes are occasionally furnished on the low r er 

 surface as well as on the upper, there is no dependance in them, since some 

 specimens have none or either : others very sparingly above and none beneath, 

 and it is only occasionally that many spines are observable. 



Names. ThornbacJc, from spines or thorns on its back : thorny, Aberdeen. 

 The young termed maids, maidens or maiden-skates : ray-maids. Morcath bigog, 

 Welsh. De Bog, Dutch. Le Baie Bouclee, French. 



Habits. It keeps to shallower water than most of the other species of the genus, 

 and is taken at all seasons. Low observes, that " skates of all kinds are taken on 

 the ordinary fishing-grounds round the Orkneys, but, like other flat-fish, are most 

 frequently met with in the eddies of the tides, or where two tides meet ; especially, 

 when the tides run strong they are obliged to withdraw to these calmer spots, 

 their shape hindering them to sustain themselves against the force of the current." 

 Mr. Dunn observes, " I have known quantities of the common thornback-ray 

 glutted with scad (Garanx trachurus), thirty miles south from the Deadmans in 

 winter, so they must have been down at the sea bottom " (Misc.). Very voracious, 

 feeding on every kind of flat-fish, is very partial to heri'ings and sand-eels, while 

 Pennant observes that it sometimes eats Crustacea, also worms and shells. 



Means of capture. Trawling, or with hooks and lines. In the Firth of Forth 

 Parnell observes that large quantities are taken during May and June, and form 

 a cheap and wholesome food to numbers of the lower classes. 



Baits. Pilchards and herrings, crabs and other Crustacea, and as it is rather 

 dainty respecting its food on a change of bait the captives have sometimes become 

 abundant. 



