86 



THE FUNDUS OCULI OF BIRDS 



circles of opaque nerve fibres are visible. 

 The whole background, including the disc, 

 seems to be dotted with many punctate 

 pigment grains. 



Canada Goose. Branta canadensis. The 

 individuals of this species examined by the 

 writer had been domesticated in the Bronx 

 Park for several years but under conditions 

 approaching their usual habitat. 



The appearances of the fundus oculi were 

 practically identical in all the specimens 

 examined, and are similar to those of the 

 Mallard. The concentric arrangement of 

 the optic fibres in Anas is lacking in the 

 Brant, while the latter has the larger pecten. 



Although the pecten is rather large, the 

 outlines of the vertically oval, yellowish- 

 white papilla are visible throughout. 



Blue (Snow) Goose. Chen c&rulescens. 

 Plate XXVII, page 147, reproduces the fund- 

 us appearances of two individuals examined by 

 Mr. Head and of another seen by the writer. 

 The backgrounds were the same in all. 

 The predominant fundal color is a distinct 

 fawn, sprinkled with small, round, orange- 

 pink dots of irregular shape and size. Run- 

 ning vertically past and parallel with the 

 optic papilla, over the lower half of the 

 fundus, are numerous, straight, orange-red, 

 choroidal capillaries. 



The fovea is probably indicated by a small, 

 glistening white dot above the end of the disc 

 on the nasal side. This small, punctate 

 deposit nearly disappears when the light 

 from the mirror is turned in certain directions. 

 An inconstant, bright-green reflex is notice- 

 able in this part of the eye, and there is a 

 decided photophobia when the ophthal- 

 moscopic light is flashed upon the region 

 of the supposed macula. Moreover, by 

 careful focusing the circumference of the 

 foveal (?) dot shows a small brown rim, like 

 the sides of a crater. However, the light 

 from the mirror does not reveal any actual 

 depression; the eyeground appears level 

 throughout and is uniform both in color and 

 texture. 



|The optic nerve-head is boat-shaped, tinted 

 orange along its central zone and shows a 

 narrow rim of coarse opaque nerve fibres 



that form a fringe about its circumference. 

 This orange centre is sprinkled with numer- 

 ous minute, dark-brown or black dots. A 

 few gray opaque nerve fibres arise from the 

 disc margins, and cross the fundus horizon- 

 tally. The pecten, of corkscrew shape, runs 

 the whole length of the disc and comes 

 well into the vitreous. 



Lesser Snow Goose. Chen hyperboreeus. 

 (Figs. 93 and 131.) There is, judging from a 

 naked-eye survey of this fundus, a grayish 

 but well-defined, rather narrow, retinal 

 band, devoid of pigment, that runs obliquely 

 through the center of the field from one 

 periphery to the other. It is more definitely 

 outlined by pigment grains on its inferior 

 than on its upper margin, especially where 

 it traverses the nasal half of its course. 

 About its middle point is the single macular 

 region and fovea — a short but regular line of 

 pigment in the center of an enlargement 

 of the band. 



The large, shoe-shaped pecten is com- 

 posed of 24 heavy, compact convolutions 

 that terminate in a cigar-shaped superior 

 and a triangular inferior extremity. The 

 conical crest of the upper free border is 

 wide for three-fourths of its entire length. 

 It terminates in a thin, corkscrew process 

 before it reaches the tip of the upper con- 

 volution, which almost touches the retinal 

 band, with which the (projected) major 

 axis of the nerve-head describes a right 

 angle. The convolutions decrease pari passu 

 in size from behind forward, all the coils 

 inclining towards the lower end of the disc. 



Pho enicopterif ormes 



Common Old-world Flamingo. Phoe- 

 nicopterus roseus. (Figs. 94 and 115; macro- 

 scopic view.) This ocular background shows 

 a small but compact penten, whose 18 

 convolutions are (apparently) drawn towards 

 the center of the organ above by a deep, 

 cigar-shaped crest, so that the marsupium 

 resembles, when viewed laterally, a truncated 

 cone. 



Stretching obliquely across the fundus is a 

 light-colored, retinal band of medium width, 

 which ends abruptly just before it reaches 



