438 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
86. Xenochirus triacanthus Gilbert. 
A single specimen dredged at station 3350, near Point Reyes, Cal., at a depth of 75 
fathoms. In life olive brown, with small pearly spots on back. 
87. Xenochirus alascanus sp. nov. 
Most nearly related to X. pentacanthus, with which it agrees in having a rostral 
plate bearing three spines and in having the branchiostegal membranes without free 
fold. It differs conspicuously in the broader head, with its much heavier spines and 
ridges, in the presence of deep postocular and nuchal pits, in the smooth breast and — 
cheeks, in the different coloration and fin rays, and in many other details. Head 44 
to 48 in length; width of head equaling or slightly exceeding length of snout and eye. ‘ 
Depth of body equals length of snout and half eye. Fin rays in eight specimens as 
follows: 
; Spinous dorsal. | Soft dorsal. | Anal. | 
Rays...---- eh ie eh Vo WS SWIG |=" veal: a7 a\emny eae 
| SPECLMONS eases seer ese 1 4 3 | 6 2 | 7 1 | 
Pectorals 15 or 16; ventrals 1, 2; lateral line 39 or 40. 
A decided pit Denia the eyes, and a deep transverse nuchal depression, the two 
separated by the prominent occipital region. Snout of moderate length, much | 
depressed behind the spines, 3? to33 in head. Eye 3 inhead inadults. Interorbital 
space wider, much more deeply concave, the supraocular ridges very heavy, minutely 
roughened, ending posteriorly in robust spines. Rostral armature as in X. penta- 
canthus, consisting of a small apical plate bearing three small diverging spines, 
behind which are two longer ones. Preorbital with a small spinous point directed 
backward. Aspine posteriorly on bony bridge across cheeks. Below this bridge 
the cheeks are entirely mailed by three rounded plates, which bear no spines, except 
in young specimens, and are so intimately joined that the sutures are difficult to 
discover. In X. pentacanthus the plates are much smaller and do not entirely cover 
the cheeks, leaving soft areas surrounding them, and the two posterior plates bear 
spines. Maxillary 3% in head, barely reaching front of orbit. Teeth on jaws, vomer, 
and palatines. The usual row of 5 or 6 prickles on eyeball. Preopercle with three 
diverging spines at angle, a rounded lobe beneath them. Spines and ridges otherwise 
as in X. pentacanthus, but stronger and rougher. Three or four strong plates present 
on gular membrane; a few weak ones, or none, on branchiostegal membrane mesially. | 
Two barbels at tip of each maxillary, and a pair, often double, on under side of 
mandible arising from the margin of the anterior pair of mandibular pores. The 
symphyseal pore has its margin sometimes provided with very short barbel-like 
elevations. 
Space between dorsal ridges very deeply concave in front of dorsal fins; the single 
ridge behind dorsal fins provided with very short, scarcely perceptible, double spines. 
Lower lateral series of plates continued forward to axil of pectorals (becoming indis- 
tinct anteriorly in X. pentacanthus). Ventral series anteriorly with few short spines 
or none; this series strongly spined in X. pentacanthus. Plates on breast arranged 
alike in the two species, but in X. alascanus they are more finely striate and bear 
neither spines nor raised centers, except in very young specimens. In X. pentacan- 
thus the elevated centers may or may not bear short spines. Seven plates before 
dorsal, 8 or 9 under spinous dorsal, 2 or 3 between dorsals, 7 or 8 under soft dorsal, 
13 or 14 behind dorsals. Distance from snout to nape equals or slightly exceeds dis- 
tance from nape to first dorsal. Front of anal under end of spinous dorsal or slightly 
behind that point, more anteriorly placed than in X. pentacanthus. Ventrals 2} to 
23 in head. Lower pectoral rays produced, with incised membranes, as long as head 
behind rostral spines. 
