19 285 



The head (PI. I, fig. 5) is flattened, the long tubiforni snout depressed and al- 

 most hexangular in transverse section. The postorbital part of the skull is flat 

 above, with deeply excavated postfrontal region (fig. 6), the interorbital part more 

 or less concave; the proximal half of the preorbital part is roof-shaped, the distal 

 half flat, the whole forming a broad and rather thin and flat beak, with sharp 

 edges and concave underside (fig. 7). The preorbital part is about 2^1-2 times as 

 long as the resi in F. labacaria, fully 3 limes in F. petimba; the greater part belongs 

 to the mesethmoid (somewhat less than ' iths); the whole terminal part (somewhat 

 more than '/i) is made up by the vomer alone (while in Aulostoma the mesethmoid 

 seen from above reaches along the middle line almost to the end of the snout). 



On the upper aspect (fig. 6) the proximal part of the mesethmoid is seen 

 forming the anterior borders of the nasal openings, while the other borders belong 

 to the prefrontals (prf); above the nasal pits are found the frontals (fr), reaching 

 far backwards, about to the posterior end of the skull, here embracing a great 

 part of the narrow supraoccipital (so); the rest of the latter is enclosed between 

 the epiotics (ep), which are coalesced behind the supraoccipital into one bone and 

 form the median "occipital" crest. In the fossa on each side of the base of the 

 latter is articulated the great ossified tendon (or muscular lateral plate) ; the some- 

 what swollen anterior, inner margins of the fossæ correspond to the knobs on the 

 epiotics mentioned in Aulostoma. The end of the "occipital" crest is connected with 

 the foremost nuchal shield. From above are further seen the postfrontals (pf), 

 pterotics (sq) and the posttemporals (pt). The latter are in this genus firmly nailed 

 with the skull, forming sutures with the pterotic, the frontal, epiotic and exoc- 

 cipital. Besides are seen from above the exoccipitals (eo), broadly meeting from 

 both sides over the foramen magnum and separated from the supraoccipital 

 through the coalesced epiotics; finally, the knob-shaped, convex condyle is seen 

 under the occipital foramen. 



Parietals and opisthotics are absent. 



From the triangular nasal groove a furrow, corresponding to that on the beak 

 of Aulostoma, runs to the end of the snout, lodging the anterior part of the supra- 

 orbital lateral line; the median part of the mesethmoid and the vomer enclosed 

 between the two furrows is elevated over the level of the lateral parts and sculp- 

 tured, the pattern being somewhat different in the species examined ; also the 

 lateral parts of the mesethmoid are sculptured with fine radiating striæ. A row of 

 slender, extremely thin tubes enclose the lateral line; no rudiment of a nasal bone, 

 like that of Aulostoma, nor any anlorbital bone is found here; the place taken 

 up by the latter in Aulostoma is in this genus occupied by the front end of the 

 prefrontal. The outer face of the prefrontal is deeply hollowed out (fig. 5, prf.); 

 the upper border of the hollow is sharply serrated in F. petimba (and depressa), only 

 crenulated in (adult) F. tabacaria. 



On the lateral aspect of the brain-case as in Aulostoma a sharp crest (partly 

 serrated in F. petimba and depressa) separates the upper from the lower surface, 

 the two articular facets for the hyomandibular (fig. 7) are in the corresponding 



37* 



