XENOMYSTAX RICTUS. 315 
Skin appearing as if roughened by imbedded scales, much larger than 
those of E. cocosa on which in fact they are hardly perceptible. 
Dark brown, with a series of small, white spots, about fifty in number, 
extending from the head to the end of the tail on each side near the base of 
the dorsal, and parallel with this series another just above the middle of the 
flank not continuing so far backward as the first. 
Hab. Cocos Islands. 
Xenomystax rictus sp. n. 
Plate N. 
Br. r. 11; D. 265-292; A. 192-214; P. 12, rarely 13. 
Elongate and moderately slender, compressed and tapering gradually to a 
slender extremity behind the body, which is subeylindrical, depth about one 
eighteenth of the total length. Head long, nearly one fifth of the total, 
narrow forward, tapering regularly from the occiput, somewhat flattened on 
the crown, half as long as the distance from snout to anal origin, three 
eighths as long as the caudal region. Snout rather long, nearly one third 
as long as the head, four times the length of the eye, extending beyond the 
lower jaw about three fourths of the ocular length, blunt and soft at the end, 
which bears a rounded patch of slender subconical teeth on its lower side. 
Eye one fourth as long as the snout, one eleventh of the length of the head, 
equal to the width of the interorbital space, little forward of the angle of 
the mouth, front edge at the posterior fourth of the length of the mouth 
cleft. Mouth wide, cleft but little backward of a vertical from the hind mar- 
cin of the orbit; maxillary ending at the mid-length of the head ; lower jaws 
shorter than the upper, a trifle swollen at the ends, where they fit upward 
into a toothless notch below the anterior nostrils. Teeth small, subconical, 
in bands which are divided lenethwise on the jaws by a groove, in a single 
series of four or more stronger hooked teeth on the vomer between the max- 
illaries, separated below the end of the snout by a wide notch from the 
anterior group. This vomerine series contains the strongest teeth; these 
extend only through the forward half of the cleft, and the series is continued 
by much smaller teeth nearly or quite to the vertical from the forward 
border of the orbit. At the inner side of the groove on the jaws, and in 
the vomerine series the teeth are rigid; all the others are depressible. 
Anterior nostril tubular, projecting above the ends of the lower jaws ; pos- 
terior subround, with raised border, half way from the eye to the anterior. 
