Capt. Portlock on the Ova of the Large Spotted Dog-fish. 345 



LI. — Further Notice respecting the Ova of the Large Spotted Dog- 

 fish (Scyllium Catulus). By Capt. Portlock, ll.E. 



Corfu, March 11,1815. 

 In my preceding note (p. 261) I have stated the general coinci- 

 dence of the drawing given by Mr. W. Thompson with the speci- 

 mens I had obtained and observed of what I also considered the 

 ova of the large spotted dog-fish, but at that time I had been unable 

 to procure the fish still having the ova in their last state of de- 

 velopment prior to protrusion undisturbed within it. On the 17th 

 of February I was more fortunate, as I obtained on that day from 

 one of the fishermen a very fine specimen, exhibiting the ova in 

 all states of development, the ovaries being loaded with ova of all 

 sizes, from the most minute up to those of three-quarters of an 

 inch in diameter, the latter being of course few in number, the 

 former abundant. Of the greater, or those equalling and exceed- 

 ing half an inch, there were at least eight, and it is probable 

 more, as the fish had been opened and the ovaries slightly rup- 

 tured before I got it, so that some may have escaped, as they 

 very readily did on my examination. These eggs were spherical, 

 and of a greenish yellow colour : when put into turpentine (as I 

 placed one), or left with the fish in a preservative mixture of cor- 

 rosive sublimate, they became flattened without further injury, 

 nearly to the thickness corresponding to the depth of the horny 

 case, which explains how bodies of such a form and size should 

 subsequently become invested with that covering. Risso draws 

 a distinction in this respect between the Scyllium Catulus (his >S'. 

 stellaris) and the /S. Caniculus, stating the former to bear sphe- 

 rical eggs of various magnitudes of a pale yellow colour, and the 

 latter the horny quadrangular eggs, as also >S^. Artedi (Risso), 

 the black-mouthed dog-fish, and it is therefore probable he only 

 saw the fish immediately after the protrusion of the horny cases 

 from the oviducts. In my specimen they were still in situ, and 

 without removing them I could measure their length and breadth 

 and even depth. The length was in this instance almost exactly 

 that of Mr. Thompson's specimens, viz. nearly 4i~ inches, mea- 

 sured to the extreme points, the breadth and depth the same as 

 those I have before stated ; the specimens appearing to vary in 

 length, but to preserve nearly the same breadth and depth. There 

 can now therefore be no doubt that Mr. Thompson has figured 

 the ova of the great spotted dog-fish, although none of my spe- 

 cimens exhibit so rough a plaiting as his figure exhibits, and the 

 colour when fresh is uniformly a horny yellow, though soon dark- 

 ening when kept exposed. The last specimens I have obtained 

 were fresh from the fish on the 27th of February. 



P.S. Corfu, March 22. — A specimen of a female was brought 

 Ann.^ Mag. N. Hist. Vol.xv. 2B 



