80 



THE FUNDUS OCULI OF BIRDS 



ends at the pigmented circumference of the 

 circular macula. 



The macular region, twice as wide as the 

 surrounding band, presents a large, central 

 fovea. 



The pecten has much the same shape as in 

 Squatarola; it is, however, a little larger, and 

 has 32 convolutions. The medium sized 

 coils, longer (taller) as one approaches the 

 posterior free margin, are capped by a deep, 

 irregular, partially serrated, ridge-like crest 

 that terminates posteriorly in a sharp point; 

 anteriorly the crest becomes much narrower, 

 and ends in a tapering triangle. 



The optic entrance is (at its middle) seen 

 through the interrupted coils of the pecten; 

 and the infulapapillary angle, made by its 

 projected major axis and the lower margin of 

 the retinal band is between 45° and 50°. 



The shape of this eyeball is oval, 10x11. 



Stone Plover. (Edicnemus scolopax. 

 The fundus appearances (left eye, erect im- 

 age) of this nocturnal bird are depicted in 

 Plate XVII, page 137. 



The eyeground is a warm brown or choco- 

 late color, rather deeply pigmented near the 

 periphery and covered with orange-red dots 

 that are very densely packed on the upper 

 half of the fundus. Below the optic entrance 

 are numerous choroidal vessels running paral- 

 lel with and on either side of the papilla. 



The macula is difficult to distinguish and is 

 not clearly defined with the ophthalmoscope. 

 It is situated above the superior end of the 

 disc on its inner or nasal side, and about half 

 the apparent length of the pecten from the 

 upper end. 



The fundus coloring is slightly darker in 

 the macular area, which is surrounded by a 

 reflex ring, pale gray in color, in the form of 

 very minute lines radiating from its margins. 

 There are, also, a few radiations near the 

 fovea centralis. 



The papilla is white, oval in shape, fringed 

 all round with dense black pigment, and a 

 few gray, opaque nerve fibres are seen on 

 either side of it. 



The pecten is very large and projects well 

 into the vitreous. It is of unusual shape, 

 rather narrow, but when examined from above 



looks as if it had been compressed and flat- 

 tened on both sides, with a narrow edge above. 



Great Bustard. Otis tarda. (Figs. 127 

 and 90.) The macroscopic reproduction of 

 this background shows a narrow fine of pig- 

 ment, representing the usual retinal band, 

 which extends horizontally across the central 

 two-thirds of the visible fundus. At almost 

 its exact middle is an incompletely oval area 

 encircled by a ring of pigment grains. A dark 

 spot (fovea) more or less surrounded by 

 black dots, occupies the centre of this crater- 

 like space. 



The large and compact pecten forms a very 

 regular, oval figure whose extremities appear 

 to be of practically the same shape and size. 

 It is made up of about 22 convolutions united 

 in a crest that, from above, takes on the ap- 

 pearance of a fisherman's (cork) floater. The 

 pecten in this species is remarkable because 

 of the small number and large size of its folds, 

 because the central five of these are the long- 

 est, and because the middle half of the keel, 

 or crest, is projected as a tall cone into the 

 vitreous. 



The major axis of this optic disc subtends 



an infulapapillary angle of 70° with the linear 



retinal band. 



Gruiformes 



Kagu. Rhinochetus jubatus. In many re- 

 spects the eyeground of this bird, as seen by 

 the ophthalmoscope, presents appearances 

 (see Plate XVIII, page 137) similar to the 

 fundus pictures (Plate XVII, page 137) of the 

 Australian Stone Plover, except that the 

 former has a gray area above the disc, instead 

 of a red and brown one. The drawing is of 

 the right eye, as seen by the erect image. 



The background is, in general, covered with 

 a mass of minute dots that are gray in the 

 upper half of the fundus and orange below. 

 The lower sectors of the fundus are stippled 

 with pigment. Choroidal vessels are numer- 

 ous and run in rather straight, vertical lines 

 on both sides of the optic disc. They are 

 dull-orange in color. 



The fovea is shown towards the anterior or 

 nasal half of the retina, and appears as a 

 round hole or crater-like depression, brown in 

 color, which reflects a grayish sheen from its 



