60 



WEALDEN AND PURBECK FOSSIL FISHES. 



scale (r.s.), which bears a median row of three or four recurved denticles rapidly 

 increasing in size backwards. The lateral wings of this ridge-scale taper down- 

 wards as they pass below the limit of the supraoccipital plate. A relatively large 

 parietal {pa.) bounds the supraoccipital outwardly or below, and tends also to 

 bound the squamosal behind. It may even be interpreted as consisting of the 

 parietal fused with a narrow supratemporal, for it is crossed by two sparse trans- 

 verse rows of large openings which mark the course of slime-canals, while a long 

 smooth digitate prominence (x.) from the middle of its hinder border may be a 

 post-temporal. The shape of the bone and its reticulate ornament are well shown 

 in an isolated specimen (PI. XIV, fig. 4) which has unfortunately been drawn 

 upside down. The squamosal bone, which has slipped a little beneath the parietal 



Fig. 23. — Microdot! radintus, Agassiz ; restoration (omitting' pterygo-quadrate arch), nearly nat. size. — 



Middle Purbeck Beds ; Swanage, Dorset. 



in the original of PL XV, fig. 1 (sq.), is relatively small, with its maximum width 

 not quite equalling its maximum length. It forms the upper part of the posterior 

 border of the orbit and completely covers the postfrontal (sphenotic). The f rentals 

 (/V.) are by far the largest bones of the cranial roof, widely expanded in their 

 rather flat hinder region, tumid above the front of the orbit where they bend 

 sharply downwards, and truncated anteriorly where the}' end above the middle of 

 the anterior border of the orbit. The course of the longitudinal slime-canal is 



