376 Mr. Rumball on the Focus of Vision. 



taken ; but there is great reason to think that it will be found 

 to offer some external characters which will distinguish it from 

 the IVJiite Beluga of the North Seas, to which the skull is so 

 nearly allied. It may perhaps be one of the species recently 

 described by Qiioy and Gaimard, as they saw them floating in 

 the water. 



This head differs greatly in the length of its beak from the 

 Delphiniis (Delphinapterus) Peronii of Lacepede, which is 

 figured by Cuvier, Oss. Foss. t. 21. f. 4 & 5, which was brought 

 home by Mr. Hunter the surgeon to the same expedition. 



The second specimen has no habitat affixed to it in the 

 Museum. It was there before my appointment. It agrees with 

 the head of Delphintis griseiis, figured by Cuvier, Oss. Foss. v. 

 t. 22. f. 1 & 2. in almost every particular; except that it has 

 1 1 teeth on each side in the upper jaw, and 10 in the lower; 

 while that species has seldom more than 2 or 3, in the lower 

 jaw only. 



In this latter character it agrees with the Delphinus Orca 

 of Otho Fabricius, the skull of which is figured by Cuvier, 

 t. 22. f. 3 & 4 ; but it diffei's from it in the small size of the tem- 

 poral fossfe and in the width of the temporal ridge and the 

 great size of the space for the attachment of the occipital 

 muscles, and also in its small size, which is even less than the 

 former species. 



Length from the tip of the beak 8 J inches; from the beak 

 of the blower to the front of the occipital hole 6 inches ; length 

 of the blower 2 inches ; breadth of the blower 2 inches ; breadth 

 of the head between the outer edge of the post-orbital apophy- 

 sis 9\ inches ; head between the wing of the temporal bones 

 8 inches ; height of the head to the occipital crest 7 inches ; 

 breadth of the beak at the commencement of the cheek-bones 

 4^ inches; length of the temporal fossae 3^ inches; breadth 

 of the attachment of the occipital muscles 7 inches. 



I propose to call this species, on account of its appearing to 

 connect two species, Delphinus intermedius. 



LX. On the Position of the Focus in the Eye. By Mr. J. R. 

 Rumball, M.U.C.S.* 



I HAVE at various times made many optical experiments ; 

 and as some of them are directly opposed to the generally 

 received opinion, " that the images of objects which enter the 

 eye, are painted in an inverted position upon the retina," I 

 hope you will not consider an account of them unworthy a 

 place in your valuable Magazine. 



* Communicated by the Author. 



I shall 



