Mr. ALpERSON on a Whale of the Spermaceti Tribe. 261 
The Chrystalline lens was nearly spherical, and rather more 
convex anteriorly than posteriorly. 
The transverse diameter measured .45 inch, 
Diameter in direction of the axis .375 
The sclerotic coat was cut into about its middie, and there 
measured .7 inch in thickness, becoming thinner as it proceeded 
forwards to join the cornea, where it turned inwards. 
Where the optic nerve enters the sclerotic coat, this latter 
only measured .5 inch in thickness, differmg in this point from 
the same part in the balena, which, according to Cuvier, is 
an inch and a half in thickness. 
The density of this coat is very great, so much so, as 
previously to its being cut into, to give the idea of its being 
formed of cartilage, or corn of bony matter. 
The internal cavity, containing the humours and the iris, 
was very small, and not of the same shape as the exterior of 
the eye-ball, on account of the varying thickness of the scle- 
rotic coat; the depth of the interior cavity, from the anterior 
part of the.sclerotic coat, measured only .8 of an inch. 
We learn from Hunter, that the pigmentum nigrum covers 
the back part of the iris, and the corpus ciliare, but that it 
does not extend farther back. I should have felt great diffi- 
culty in stating its limits, as the sclerotica was certainly tinged 
with it posteriorly to this part. 
The tapetum presented a very beautiful appearance ; its 
color was a green, formed by an admixture of blue and yellow, 
with a slight predominance of blue; it was speckled with 
lighter colored spots throughout. 
Posteriorly to the transverse axis of the eye, was inserted 
into the sclerotica a thick mass of muscle, enveloping the optic 
nerve. This mass was itself enclosed in a dense fibrous sheath, 
LL2 
