294 PROCEEDINGS OF THE ACADEMY OF [April, 



advance of the latter. P. very long, reaching the origin of the 

 D. V. very long, reaching half-way in the space between their 

 own origins and the base of the caudal. 



Hemiexocoetus caudimaculatus ^p- ""v. 



No. 7,508. Type." Taken in lat. 23° N. long. 106° W. 

 (Mazatlan, Mexico). Dr. William H. Jones. 



The form of the body is somewhat elongate, moderately com- 

 pressed, with the sides more or less rounded, and with the dorsal 

 and ventral profile lines equally convex. The greatest depth of 

 the body is nearly median, and it is contained in the total length 

 (exclusive of the beak and the caudal; about six times. The 

 head is large and compressed, not veiy broad above, and contained 

 in the body (as measured before) about four times. The eye is 

 large and superior, and it is contained in the head (exclusive of 

 the beak) about three times. The eye is also greater than the 

 interorbital space. The mouth is small and superior, and fur- 

 nished with minute teeth. Opercles large. The origin of the P. 

 is superior, level with the upper part of the eye, and near the 

 branchial aperture. Branchial apertures large. The P. are 

 exceedingly large and long, reaching at least to the origin of the 

 D., and thus for about half the length of the V. The origin of 

 the V. is nearer the branchial aperture than the base of the caudal, 

 and the fins reach posteriorly for at least half the distance between 

 their own bases and the base of the caudal. The origin of the 

 D. in advance of that of the A., the fins similar, but the longest 

 rays of the former equal to the depth of the body at that point. 

 The general color of the body is a rich plumbeous brown above 

 and silvery beneath. The upper or outer rays of the P., except 

 the first, are blackish. The first ray of the P., together with the 

 5 basal rays, white. D. and A. brownish. V. edged upon the 

 outer and inner rays with white, the inner rays blackish like the 

 same of the P. Caudal whitish, except the bases of the rays and 

 the jet black spot upon the outer portion of the lower lobe. The 

 body was covered with rather large scales, but as the squamation 

 is injured I am unable to give any count. Traces of a lateral 

 line existed upon the inferior scales along the sides of the ventral 

 region. D. 10, A. 11, P. 11. 



This small example measures 25 mm. from the tip of the upper 

 jaw to the base of the caudal. 



