84 WHITEATES ON FOSSIL FISHES FROM 



wMch it happens to be preserved. The upper margin of the posterior suborbital is 

 angular in the middle (immediately opposite the transverse suture which divides the 

 frontal from the parietal plate) and subangular at both ends, while at each side of the 

 central angle the margin is shallowly concave. Its lower margin is nearly straight in 

 front and rounds up obliquely behind. 



The precise contour and exact location of the third suborbital are not satisfactorily 

 shewn in any of the specimens of E. Foordi collected by Mr. Foord. In specimen No. 1, 

 a longitudinal but slightly concave suture appears to cvit off a small plate, which may 

 represent the third suborbital, from the anterior portion of the lateral margin of the 

 frontal plate, but this supposed suture may be only one of the superficial surface markings, 

 of even a mere accidental crack in the frontal plate. Immediately above the space 

 originally occupied by the eye, in si^ecimen No. 4, there is a small narrow plate, which 

 also may represent the third suborbital, but the exact shape of this plate is not well 

 shewn, and it may have been misplaced. 



The maxilla is long, narrow and j)ointed at both ends. Its lower or tooth-bearing 

 margin is nearly straight, and its upper margin is slightly expanded a little behind the 

 midlength. It is bounded in front by the posterior termination of the premaxillary 

 portion of the frontal plate, and above, partly by the entire lower margin of the inferior 

 suborbital, and partly by the anterior half of the lower margin of the prœoperculum, 

 which is shallowly and somewhat obliquely excavated for its reception. 



The so-called prœoperculum (the supratemporal of Huxley) is a large plate which 

 covers most of the cheek. It is rather irregular in shape, but may be described in a 

 general way as a somewhat five-sided plate, which is longer than broad, as well as 

 pointed near the middle in front and at the base behind. Its front margin is acutely 

 pointed a little below the middle, where it fits into the angle formed by the infero- 

 posterior margin of the posterior suborbital with the posterior margin of the inferior sub- 

 orbital ; its lower margin is nearly straight behind the centre, where it forms a continuous 

 line with the lower margin of the maxilla, and shallowly excavated in advance of the 

 middle, as already stated, for the reception of the posterior end of the upper portion of 

 the maxilla. The upper margin of the prseoperculum is bounded by and suturally con- 

 nected with the posterior half of the lateral margin of the parietal plate ; and the posterior 

 margin of the former, which is obliquely subtruucated but somewhat flexuous, is bounded 

 by the anterior margins of the operculum and suboperculum. 



The operculum is considerably higher than long, and its anterior margin is shallowly 

 concave. Its upper margin is somewhat narrowly rounded, its posterior border is 

 obliquely convex, and its lower margin is convex in front and concave behind. 



The suboperculum, which is placed immediately below the operculum, with which 

 it is suturally connected, is a little longer than high, and its anterior margin is also 

 shallowly concave. Its posterior and lower margins unite to form one broadly convex 

 and nearly semicircular curve, and its upper border is concave in front and convex 

 behind. In their natural position these two plates are so closely united as to look almost 

 like one large and beau-shaped plate, and in every respect are closely similar to the cor- 

 responding plates in the recent Lepidosteus osseus. 



In most of the specimens of Eusthenopleron in the Survey collection, such as Nos. 1, 

 3j^ 6, and a few others not specially enumerated, the lower jaw is seen in profile only, and 



