74 WEALDEN AND PURBECK FOSSIL FISHES. 



Description of Specimens. — -The type specimen (PL XVI, fig. 3), though 

 deepened a little by crushing, shows the general proportions of the fish and the 

 origin of all the fins. The jaws of the left side, seen from within, are in their 

 natural position ; but the broken roof of the skull is displaced upwards and exposed 

 from beneath. The calcified vertebral rings, though crushed and broken, are 

 distinct; and the scales, somewhat scattered, are well displayed both in outer and 

 in inner view. Though imperfect, the remains of the anal fin prove that it must 

 have been comparatively small. 



More or less fragmentary examples of this species are common in the Lower 

 Purbeck Beds near Tisbury, Wiltshire, and the scattered remains are interesting 

 as showing well several osteological characters of the fish. All the external bones 

 appear to have been ornamented with large flat tubercles of ganoine, which are 

 often variously fused into a vermiculating pattern (PL XVI, fig. 7), sometimes into 

 a continuous film. As seen from below in one specimen (PL XVI, fig. 4, pa.) the 

 parietal bones are longer than wide ; and as seen also from above in another 

 specimen (B. M. no. P. 9107 b), they are united in a very wavy median suture. 

 The frontal bones (/?*.) are slightly more than twice as long as the parietals, 

 excavated laterally by the large orbit, and ending in front rather bluntly. The 

 external ornament seems to be confined to their posterior half (B. M. no. P. 9436). 

 A long and narrow squamosal {sq.), bearing an extended hyomandibular facette, 

 bounds the parietal on each side. The parasphenoid is relatively large and 

 expanded (B. M. no. P. 9107 6). The cheek is covered both by postorbital and 

 by circumorbital plates. The upper postorbital is relatively large, deeper than 

 wide, widest below. The large lower postorbital exhibits a few short branches 

 radiating backwards from the curved slime-canal (Mus. Pract. Geol. no. 28441). 

 The circumorbital ring is narrow, including three or four plates above the orbit 

 (co.) and one behind. These plates are marked with the usual coarse ornament 

 (B. M. no. P. 9436). The hyomandibular is a deep and narrow lamina of bone, 

 with a large process for the support of the operculum. The maxilla seems to have 

 been long and slender, but its precise shape is unknown. The premaxilla (PL XVI, 

 fig. 5) forms a large irregular expansion, pierced near its upper border by a small 

 foramen, and produced upwards into a short and slender ascending process. The 

 oral margin bears a row of styliform teeth smaller than those of the dentary. 

 The lower jaw (PL XVI, fig. 6) is much elevated in the short coronoid region, but 

 the tooth-bearing part of the dentary is long and slender. Its outer face is marked 

 by a row of large openings of the slime-canal, and its slender styliform teeth are 

 arranged in a close series. There seems to have been a splenial with minute teeth 

 (B. M. no. P. 3608). The occiput is overlapped behind by a single pair of supra- 

 temporals as in Amia (PL XVI, fig. 4, st). The operculum is not much deeper 

 than wide, and its inner face bears a large facette for its suspension ; the coarse 

 ornament on its outer face (PL XVI, fig. 7) tends to radiate from this point. The 



