192 



Numerous empty alveoli are to be found in all the jaws of this genus, in 

 which examination will often detect the apex of the crown of the young 

 tooth. 



All the bones of the palatine arch are present in this genus. The 

 ectopterygoid is curved and concave on its lower border ; the pterygoid is, 

 on the other hand, thickened and concave on its upper border, where it is 

 also strongly beveled outward, forming the inferior internal boundary of the 

 orbit. The metapterygoid is a large, flat, and thin bone, joining the greater 

 part of the superior border of the quadrate. It does not inclose a foramen 

 with the other bones of the arch as is seen in Characinid fishes. These 

 bones are all in place on a block, which also contains pectoral spines of Por- 

 theus. On another block of the same specimen, the bones of the cheek are 

 exhibited in connection with the quadrate. One is a greatly-expanded, thin 

 bone, with the middle portion of its surface coarsely pitted. It is adjoined 

 by a much smaller laminar bone of an irregular, semi-discoid form, with the 

 middle of the convex side with three obtuse processes separated by fissures. 

 The corresponding bone in P. mohssus is figured in Plate XL, fig. 9. The 

 interoperculum is a subparallelogrammic bone, with an open sigmoid artic- 

 ular surface at one end. In P. mohssus, there are two short articular faces 

 on the other end. There is, therefore, no doubt, a suboperculum, though I 



have not identified it. 



The proximal part of the 

 hyomandibular of another large 

 specimen displays a continuous 

 narrow articular surface for the 

 pterotic. The posterior portion 

 is a protuberant condyle ; the 

 middle part narrower and con- 

 cave; the anterior part truncate, 

 and presenting forward. Not far 

 below the proximal end, on the 

 posterior border, is a condyle for 

 the operculum. It is sessile and 

 not very protuberant, and is a 

 vertical oval in outline. This 

 bone closely resembles the cor- 

 responding one of Ichthyodectes anaides. 



An incomplete skeleton of another Portheus includes pectoral arch and 

 spines, branchial arches, etc. The arches are extended posteriorly, and the 

 inner surfaces of the branchihyal bones are covered with minute teeth en 

 brosse, and support a few tuberosities. The branchial fringe is preserved, 

 consi&ting of long and slender processes. 



<s 



Fig. 9. — Femoral bones and ventral fin of a ? Portheus: 

 right-band upper figure, from above ; lower figure, from 

 the right side ; left-hand figure, from below. 



