48G FISHES OF THE FIRTH OF FORTH. 



Raia clavata.* — The Thornback. 



Specific Characters. — Upper surface very rough ; one row of spines 

 down the line of the back. (Plate XLII.) 



Description. — From a female specimen twenty inches in length, tail 

 included. Form of the body rhomboidal, similar to that of the spot- 

 ted-ray ; its transverse diameter equalling the space between the tip 

 of the snout and half-way down the tail ; from the point of the snout 

 to the tip of the pectoral, from thence to the lower point of the anal 

 fin, equal ; from the base of the anal to the tip of the tail about the 

 length of the anterior margin of the pectoral ; from the tip of the 

 snout to the temporal orifices one-third of the length, as far as the 

 termination of the base of the anal fin. Colour of the back of a blu- 

 ish-grey, with a number of ill-defined, large, whitish spots scattered 

 over the pectorals, liable to great variations. In some examples 

 there is a large ocellated spot on each side of the dorsal line. Under 

 surface pure white ; snout obtuse, slightly projecting beyond the 

 anterior margins of the pectorals ; the outline of the anterior border 

 of each pectoral sinuous ; the posterior border slightly rounded ; 

 ventrals small, placed between the commencement of the anals and 

 the termination of the pectorals, their length about three times longer 

 than their breadth ; anal rounded at the outer margin, and ending 

 below in a free point, furnished with about twenty rays, of which 

 the last is rather the longest. Dorsal fins two, rather remote, nearly 

 of equal form and size ; placed on the lower portion of the tail ; their 

 posterior margins rounded and somewhat free. Caudal fin rudimen- 

 tary, nearly half the length of the base of the second dorsal. Eyes 

 about the size of the temporal orifices ; mouth situated beneath, 

 teeth blunt, arranged in several oblique rows in each jaw. (In the 

 females both young and old, the teeth are always blunt, allowing the 

 finger to be passed freely over them in any direction ; in young 

 males the teeth are also blunt ; but in adult specimens they generally 

 become long and very sharp.) Body on the upper surface very 

 rough, covered with minute spicula, besides a number of large spines 

 with broad bases ; these spines however are very variable, in dif- 

 ferent individuals, both in number and position ; in some examples 

 they are nearly altogether wanting ; but the series along the middle 

 line of the back and tail is almost always present. 



In the specimen now before me, there is one spine on the 

 upper surface of the snout ; one on each side a little farther 



* Rata clavata, Cuv., Yarr., Jen., Mont., Penn., Flem. Maiden Skate. 

 Scotland. 





