282 Papers from the Marine Biological Laboratory at Tortugas. 



The relative positions of the various parts of the head may be more 

 readily understood by reference to figure 13, plate vi, which is a lateral 

 view of the same fish whose head is shown in figures 15 and 19, plates vi 

 and VIII. Clearly brought out are the lateral positions of both eye and 

 spiracle, and the elongated form of the latter with its valve. This valve is 

 hinged on the roof of the opening in such manner that it swings upward, 

 inward, and backward into a recess to open the spiracle. The semilateral 

 position of the gill-slits, especially of the anterior ones, should be noted. 

 These in the ordinary rays are ventrally located, while the eyes and spiracles 

 are dorsal. 



A better view of the head and snout is shown in figure 12, plate vi, a 

 photograph of the same fish shown in figure i, plate i. It has the pectoral 

 hanging down and the throat is supported on a small box to keep the mouth 

 clear. Attention is particularly called to the color of the snout, the spots 

 on the head, the position of the spiracle at the junction of pectoral fin and 

 head, and the eye with its vertical pupil immediately over the mouth. 

 The snout of Coles's specimen No. i for 1912 (fig. 9, plate v) does not show 

 very well. However, the spiracle with its spots is well brought out. 



These are the only lateral views of the head of Aetobatus known to the 

 writer. In the course of this research, however, a similar view has been 

 found of the head of another eagle ray. In figure 21, plate vii, is shown the 

 head of Miklouho-Maclay and Macleay's spotted ray, Myliobatis punctatus 

 (1886). If comparison of this be made with the preceding figures, marked 

 differences will be seen. The snout is long and slender and curiously 

 upturned at the tip. The spiracle bears the same relative position to the 

 pectoral as in Aetobatus, but the eye is considerably further forward, though 

 still over the mouth. 



Figure 16, plate vi, is a "head on" view of the ray lying on a table with 

 the throat supported on a small box to keep the under parts of the head clear 

 of the table. The points of interest shown in this figure are the nasal 

 openings, the color on the snout, the spots on the forehead, the eyes placed 

 laterally with the ball just below the line dividing dorsal and ventral 

 surfaces, the semilateral position of gill-slits, and the size and position of 

 the "wings," the pectoral fins. Above all the figure shows how the ray 

 justifies its name, Aetobatus, eagle ray. Another attractive figure is No. 10, 

 plate V, made from one of Mr. Coles's admirable photographs of his ray 

 No. I, 1 91 2, taken at Cape Lookout. Attention is called to the relative 

 position of spiracles and eyes, to the sink in the head over the brain, to the 

 white streaks under the eyes, to the dark and spotted nose, and to the spots 

 thickly scattered over the head. 



Before leaving the subject, it may be well to refer to the structure of the 

 head and snout shown in various other figures reproduced in this article. 

 Dumcril's (1861) elegant figures are shown in figure 8, plate iv. Figure A is 

 A. latirostris; B \sA. narinari; while C is A. flagellum. All these are plainly 

 drawn from preserved specimens, as the shrunken parts show. All three 



