Eyelids and Lachrymal Apparat us of Birds. 
11 
In the study made by Slonaker and the writer on the eye of the 
Sparrow and other Birds they found Slonaker’ s marginal plait (see 
cut) not only in numerous sections of the Sparrow’s third lid, but 
in all the other Birds so far examined; it is certainly well marked 
in such unrelated species as the Sooty Tern, the Red-Headed Wood- 
pecker, and in various Pigeons. Strange to say, Fumagalli (Ueber 
die feinere Anatomie des dritten Augenlides, International. Mon- 
atsschr. fur Anatomie und Physiologie, Vol. 16, p. 129, 1899) 
makes no mention of this important structure, and, although the 
wdiole subject is by him elaborately illustrated by well executed 
L<i 
Fig. 5 — Section of the Third Eyelid of a Pigeon, Showing Especially 
Slonaker’s Marginal Plait. 
The upper picture is from the work of Fumagalli, the lower as found 
by Slonaker-Wood. 
plates, he pictures the Pigeon’s accessory eyelid as lacking in the 
marginal plait. 
All vertebrates possess at least six extraocular, bulbar muscles — 
four recti and two obliques. Birds have two more (that control the 
movements of the third eyelid) viz-. : the quadratus muscle and the 
pyramidalis, which are inserted into the posterior hemisphere, be- 
hind the scleral insertion of the recti muscles. 
Confirming the observations of Kalt, ( Encyclopedic Francaise 
d’Ophtalmologie , Vol. Ill) and others, Slonaker and the writer 
