278 Bashford Dean Memorial Volume 



The eyes are placed so as to look laterally and somewhat dorsally. When the head is 

 viewed from above they are nearly invisible. Set in oblong apertures, with overhanging 

 brows, devoid of eyelids and even of the nictitating membrane found in many sharks, the 

 eyes of Chlamydoselachus have a fierce, staring expression like that of some snakes (see 

 Plate II, figure 6). 



We have stated above that Chlamydoselachus lacks eyelids as do all sharks known 

 to us. Garman does not in any way refer to eyeHds, simply noting the absence of the 

 nictitating membrane, the so'called "third eyelid. '' However, Mrs. Hawkes (1906, 

 p. 966) says: 



There are both upper and lower eyelids, but no nictitating membrane. The infolding 

 of the skin in both cases is sudden and distinct, that of the lower Lid is remarkable for its depth, 

 extending almost to the back of the eye. The infolded membrane both above and below 

 the eye is deeply pigmented, the lower being also provided with fine scales. This pigmenta- 

 tion, which on the under side of the eye is as deep as that of the surface of the body, together 

 with the presence of scales, indicates that the infolded portions become, at times (that is 

 when the eye is protruded), a part of the superficial skin. Those portions of the inner surface 

 of the eyehds which are never evaginated are quite smooth and of a Hght colour. The eye 

 can easily be protruded, and when in this position does not look outwards but upwards, 

 a position made possible by the large conjunctival fornix. It is known that Chlaynydoselachus 

 is a deep-sea fish, in which case an eye which could look upwards would be of the greatest 

 advantage. 



On this point Allis (1923, p. 150) states that: "This [subdermal] membrane [which 

 bridges over the space between the antorbital and postorbital processes] and the over- 

 lying dermal tissues form, in Chlaynydoselachus, the upper eyelid of the fish, and when the 

 eyeball is rolled upwards its dorsal half, approximately, lies beneath this tissue, the ventral 

 portion of the eyeball being exposed in the small external opening of the eye." No writers 

 listed in our bibliography, other than Hawkes and Allis, refer to such an eyelid. 



Here is what we find in our four adult heads. The external opening of the eye, 

 corresponding roughly to the palpebral aperture in man, is oblong and its edges are sharp 

 and distinct. In every case (in our preserved specimens) where the eye is rotated upward, 

 the cornea in this position is almost completely hidden, and the greater part of the exposed 

 portion of the sclera is covered with shagreen. Even in our preserved specimens, slight 

 pressure from below with the finger is sufficient to rotate the eye completely upward, so 

 that the cornea is entirely hidden. We infer that this fish, presumably a bottom-dweller, 

 usually has its eyes turned somewhat upward. Evidently Chlaynydoselachus does not 

 close his eyes by means of lids, but by rotating the eyes upward until the cornea is hidden 

 leaving the shagreen-covered sclera to afford protection to the eyeball. We find no struc- 

 tures in the eyes of Chlaynydoselachus that seem able to function as lids. We agree with 

 Allis (1923, p. 150) that there is probably Httle if any real protrusion of the eyeball due to 

 change of its position. 



