202 



C. H. DANFORTH. 



individuals of 170 mm. and over the organ is much more truly 

 spatulate in outline. With the exception of the specimen under 

 consideration, the width of the rostrum was found to be relatively 

 greater in the small fish than in the larger ones, but width of 

 snout and contour are not very closely correlated so that some 

 rather wide snouts are not very spatulate in outline. 



The length of the rostrum at different ages is shown in the 



FIG. i. Lateral view of a specimen of Polyodon s/>a//n</a measuring 74 mm. 

 total length. 



accompanying table based on measurements of twenty specimens, 

 ten varying in length from 74 mm. to 200 mm., and ten from 

 1,000 mm. to 1,300 mm. Intermediate stages were not available. 

 In this table the second column gives the total length from tip 

 of snout to tip of tail, the third gives the length of the rostrum 

 measured from its tip to a line passing between the anterior 

 corners of the eyes, and the fifth column show's the width of the 

 rostrum at the beginning of its distal third. The decimals in^he 



FIG. 2. Ventral view of the specimen shown in Fig. i. 



sixth column are obtained in each case by dividing the length 

 of the rostrum by the total length of the fish. Professor Stock- 

 ard 1 measured in this way a number of adult Polyodon from 24 

 in. (about 600 mm.) to 69 in. (about 1,725 mm.) and found an 

 interesting correlation between the size of the fish and the length 



J Stockard, Charles R., "Observations on the Natural History of Polyodon 

 spathula," Amer. Nat., Vol. XLI., pp. 753-766, 1907. 



