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, w^iite spots, about fifty in number, 

 extending from the head to the end of the tail on each side near tlie 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 subcylindrical, 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 fourtlis of the ocular length, blunt and soft at the end, 

 which bears a rounded patch of slender snbcouical teeth on its lower side. 

 Eye one fourth as long as tlie 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- 

 gin 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 lengthwise on the jaws by a groove, in a single 

 series of four or more stronger hooked teeth on the vomer between J:he 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 tubiflar, projecting above the ends of the lower jaws ; pos- 

 terior subromid, with raised border, half way from the eye to the anterior. 



