438 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



86. Xeuochirus 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. Xeuochirus alascanus si>. nov. 



Most nearly related to A'. }>entuca)iihun, with which it agrees in having a rostral 

 plate bearing three spines and in having the brauchiostegal membranes without free 

 fold. It differs conspicuously in the broader head, Avith 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 tin rays, and in mau3' other details. Head 4^ 

 to 4J 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 : 



Rays 



Specimens . 



Spinous dorsal. 



Soft dorsal. 



Anal. 



VI 

 4 



VII 

 3 



Pectorals 15 or 16; ventrals i, 2; lateral line 39 or 40. 



A decided pit behind the eyes, and a deep transverse nuchal depression, the two 

 separated by the i^rominent occipital region. Snout of moderate length, much 

 depressed behind the spines, 3* to3jf in head. Eye 3 in head in adults. Interorbital 

 siiace 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. A spine 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 diflBcult to 

 discover. In X. imntacanthus 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 brauchiostegal 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 A', pentncaiifhtin). Ventral series anteriorly with few short spines 

 or none; this series strcmgly spined in X. peniacanthns. Plates on breast arranged 

 alike in the two species, but in A', alascanus they are more tinely striate and bear 

 neither spines nor raised centers, except in very young specimens. In X. pentacan- 

 thu8 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 S 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 i)oint, more anteriorly phu^ed than in X. pentaeanihus. Ventrals 2J^ to 

 2J in head. Ivower pectoral rays jiroduced, with incised membranes, as long as head 

 behind rostral spines. 



