490 DR. GUNTHER ON THE FISHES OF CENTRAL AMERICA. 
289. BALISTES FRENATUS (Lacép.). 
A specimen, 8 inches long, obtained by Capt. Dow at Gonzalez Island, differs in 
being of a more uniform coloration, the yellow band on the head being but slightly 
indicated. 
292, LEPIDOSTEUS TROPICUS. 
Atractosteus tropicus, Gill, Proc. Ac. Nat. Sc. Philad. 1863, p. 172. 
D. 10-11. A.11. EH. lat. 54. L. transv. 8/12. 
The length of the head is nearly one-fourth of the total; the width of the inter- 
orbital space is two-fifths of the length of the snout, which equals the distance of the 
front margin of the orbit from the fifth scale of the lateral line. The root of the 
ventral fin is nearer to the base of the caudal than to the end of the snout. 
Two examples, 18 inches long, were obtained by Mr. Salvin at Huamuchal. 
293. MUSTELUS DORSALIS. 
Gill, Proc. Ac. Nat. Se. Philad. 1864, p. 149. 
“Teeth unicuspid. The posterior angle of the first dorsal fin projects to the vertical 
of the origin of the ventrals, although the anterior fourth of the base of the fin is above 
the pectoral. The caudal fin equals the distance between the snout and third branchial 
aperture; and its terminal lobe nearly equals a third of the length, and is obliquely 
truncated behind.” 
Panama. 
295. CARCHARIAS MACULIPINNIS. 
Isogomphodon maculipinnis, Poey, Repertor. Fis. Nat. Cub. 1865, p. 191. 
This species belongs to the subgenus Prionodon. Teeth with the terminal portion 
much constricted—the serrature being very fine, and only in a few distinct to the point ; - 
there are twelve on each side of the upper jaw; teeth of the lower jaw without any 
denticulations. The length of the snout, from the front margin of the mouth, is not 
much less than the width of the cleft of the mouth; the latter very deep, forming 
nearly a semicircular arch. ‘The dorsal fin commences opposite to the inner posterior 
angle of the pectoral; pectoral pointed, not twice as broad as long. Coloration uniform 
grey, tips of most of the fins black. 
One example, 4 feet long, was obtained by Mr. Salvin at Chiapam ; the species was 
first described from a Cuban specimen. 
297. RHINOBATUS LEUCORHYNCHUS. 
The anterior nasal valve is not prolonged to the inner angle of the nostril. Disk 
longer than broad; the preenasal part of the snout is not so long as broad at the base, 
but longer than the distance between the front extremities of the nostrils. Skin very 
