[]0 WEALDEN AND PURBECK FOSSIL FISHES. 



of the two is also deep (see PI. V, figs. 6, 8) ; and the five lower circumorbitals 

 (co.) are relatively large and deep, followed in front by the still deeper and 

 narrower plates of the preorbital series (PI. V, fig. 8, and PI. VI, pro.). The upper 

 plate of the postorbital series (best seen in PI. V, fig. 7, ]>(>.), articulating with the 

 middle part of the squamosal border, is in contact with both the posterior npper 

 and the upper posterior circumorbital plates, and bonnds above the relatively 

 large principal postorbital plate. This element (PI. V, figs. 6 — 8 ; PI. VI ; j>o.) is 

 about twice as deep as broad, of irregularly rhomboidal form, with the postero- 

 inferior angle rounded, and its outer face sparsely ornamented by tuljercles of 

 ganoine, which tend to elongate by irregular fusion. There is no clear evidence of 

 other cheek-plates of the outer or postorbital series; but in the original of PI. VI, 

 and in another specimen in the Museum of Sherborne School, there are fragments 

 which may perhaps be interpreted as representing comparatively thin plates below 

 the large postorbital continuing this series downwards and forwards. 



The mandibular suspensorium is inclined forwards so that the quadrate articula- 

 tion is ])eneath the middle of the orbit. The hyomandibular (PI. V, fig. 10) is a 

 thin lamina of bone, slightly more than twice as deep as wide, and strengthened on 

 its outer face by a longitudinal ridge, from which a cross-ridge arises at the level 

 of the prominence for the support of the operculum. The quadrate, not yet clearly 

 seen, must also have been a delicate bone, while the eiitopterygoid and meta- 

 pterygoid are comparatively thin laminse (as shown in B. M. no. P. 5591). The 

 ectopterygoid, however, is stout and horizontally expanded for the support of at 

 least three rows of teeth parallel with the outer border. Its outer face (PJ. VII, 

 fig. 1 a), which is conspicuous in several specimens, is smooth and flattened or very 

 slightly concave, appearing as a narrow band, with the oral border gently concave 

 and the upper anterior and posterior angles rounded off. This face is mistaken for 

 that of the maxilla in the restoration published in the ' Catalogue of Fossil Fishes 

 in the British Museum,' pt. iii (1895), p. 95, fig. 22. The horizontal extension of 

 the ectopterygoid (PI. VII, fig. 1) is widest in front, where its bevelled end passes 

 under the hinder margin of the equally expanded but relatively small and thin 

 palatine element (well seen in the specimen in Sherborne School Museum). Its 

 clustered teeth, as also those of the imperfectly known vomer, are relatively larger 

 and stouter than the ectopterygoid teeth. The maxilla (PL VI, ni.r.) is a delicate 

 smooth lamina of bone, deepest and rounded behind, tapering forwards .and 

 terminating in front in a slender, inwardly directed process for articulation with 

 the palatine. Its oral border, at least in the middle and anterior portion, bears a 

 spaced series of comparatively small and slender teeth (some seen in B. M. no. 

 42o08) ; while the upper border of its hinder expansion is capped by a single long 

 and narrow supramaxilla (seen in PI. VI). The premaxilla (PI. V, fig. 1 1), seen in 

 position in PI. V, fig. 7, and in PL VI {i)iihv.), is a stouter smooth bone occupying 

 only about half as much of the oral l)order as the maxilla, but bearing a regular 



