SERRIVOMER SECTOR. 321 



SO evident on the upper jaws. Vomerine teeth much larger, blade-like, in 

 two series, the teeth of which alternate to form what at first sight appears 

 to be a single, compressed serrate row, extending much forward of the max- 

 illaries, decreasing in size to very small in the anterior half of their extent. 

 In the posterior half of the vomerines each tooth is thin, wide, more than 

 twice as high as wide ; the outline" of the basal portion is subquadrate, 

 of the apical portion an isosceles triangle about one and one half times 

 as high as wide, or of the portions taken together something of an arrow- 

 shape ; posteriorly the series end near or upon a vertical through the 

 posterior nostril. The compressed teeth in the outer row on the jaws 

 resemble the apical portions of the vomerines, but the outline more nearly 

 forms an equilateral triangle. Eye moderate, one sixth to one seventh as 

 long as the snout, one seventeenth of the length of the head. Nostrils 

 small, near the eye and on the level of its upper edge, anterior with a short 

 tube. Four gills; laminas short; rakers absent; openings wide, about three 

 times as wide as the eye, low on the side, descending forward; membranes 

 united, joined to a thin partition attaching them to the isthmus. 



The skeleton of Serrivomer presents a number of peculiarities more or 

 less divergent from what obtains in allied genera, as may be seen on Plate 

 LXIII. figs. 2-5. The acquisition of the acuminate snout has been attended 

 by extensive cranial modifications, as compared with other fishes. Some of 

 the bones of the skull have disappeared, and others have consolidated to 

 such an extent that their identity is not readily established. The maxilla- 

 ries, sphenoids, vomer and frontals account for about all the elements pres- 

 ent in the preorbital section of the skull ; intermaxillaries, nasals^ prefrontals, 

 palatines and suborbitals have vanished. The upper teeth are vomerine and 

 maxillary, the former of both sectorial and raptorial teeth, the latter of rap- 

 torial teeth mainly. The preoperculum is somewhat elongate and in the 

 posterior half is rather broadly expanded into a very thin sheet ; the oper- 

 culum also is thin and broadly expanded down and backward ; the inter- 

 operculum is slender elongate and pointed anteriorly and is broadened and 

 thin backward, and the suboperculum has been reduced to membrane or is 

 absent. In the throat the glossohyal is long and pointed ; the urohyal is 

 subtriangular, thickened and heavier at the base, and tapers to a point below, 

 at the attachment of a strong tendon passing back under the basibranchials : 

 stylohyal, epihyal, ceratohyal and basihyal are consolidated ; and the bran- 

 chiostegal rays are very long slender and hair-like aiul curve upward near 



