Holt and Calderwoob — Report on the Rarer Fishes. 385 



appreciation of this circumstance has given rise to some of the existing confusion 

 in the arrangement of the genus. 



{d.) The Teeth. — That the shape of the teeth varies according to the sex of the 

 individual in several members of the genus is a fact to which reference has 

 ferquently been made, yet it has been too often left to the reader to discover for 

 himself that this statement is often only applicable to adults. A young male, in 

 fact, possesses teeth which usually differ in no important respect from those of a 

 female, and it is only with the assumption of sexual maturity, pari passu, with the 

 elongation of the claspers, that the teeth begin to show the elongated and pointed 

 characters which are so conspicuous in the adult males of some species. Even in 

 the several long-nosed species, which have the teeth pointed in both sexes, the 

 points are slightly the longer in adult males. It seems therefore by no means 

 improbable that these structures subserve some definite function in connection 

 with sexual activity. 



The number of rows in which the teeth are arranged is a character usually 

 made use of in specific diagnosis ; but it is one which possesses absolutely no value 

 unless the size of the specimen is also stated, since the number varies with the age 

 or size of the individual. As far as we are aware, such information is nowhere 

 forthcoming. The result is therefore rather confusing. The difference in the 

 number of rows at different stages may be illustrated by the statement that 

 whereas a full-grown Homelyn (/?. maciilata) has over 50 rows, an example of 

 the same species only 4 inches across the disk has less than 30 rows. Again, 

 it is not invariably stated which jaw is referred to in the enumeration, but 

 this is not of great importance since the number does not differ very greatly. 

 However there are usually a few more rows in the lower than in the upper jaw. 



Raia batis, Linnaeus. The Grey Skate. (Deep-sea.) 



Baia batis, . . . Strom, " Norsk. Vid. Selsk. Skrift.," 1881, p. 80 ; 1884, p. 46. 

 ,, ,, ... CoLLETT, " Nyt. Mag. f. Naturvid.," xviii., p. 119. 

 „ „ ... Holt, " Sci. Proc. Roy. Dub. Soc," vii., pp. 121, 219. 



A small example was trawled on the 4th July, 1890, at 220 fathoms off Achill 

 Head. Two, measuring 28 inches in length, were taken on 10th July, 1890, at 

 500 fathoms in the same neighbourhood, as was also a fine specimen of 54 inches, 

 on 20th April, 1891, in 154 fathoms. None of these specimens were preserved, but 

 they were carefully examined by one of us at the time of capture, and belonged, 

 without doubt, to the species indicated. It is noteworthy that R. circularis is the 

 onl}' ray which has been found at a depth exceeding 500 fathoms. The grey 

 skate has been taken on the Norwegian coast at a depth of 150 fathoms, and, 



TEAKS. EOr. DUB. SOC, N.S. VOL. V., PAET IX. 3 K 



