PLATE XXI. 



Pig. Page. 



1. Syllsemus anglicus (Dixon) ; head, left lateral aspect. — Chalk; Guildford. 



Enniskillen Collection (B. M. no. P. 4246). evpt., entopterygoid ; 

 eth., mesethmoid ; or., orbitosphenoid ; jw.s., parasphenoid ; pop., 

 preopercnlum ; qu., quadrate. 90. 



2. Ditto ; region of left pectoral fin, with front view of part of left clavicle 



(2 a). — Zone of Holaster subglobosus ; Blue Bell Hill, Burham, Kent. 

 S. J. Hawkins Collection (B. M. no. P. 6532). cl., clavicle; pc, pre- 

 coracoid arch; pel., postclavicular scale; pet., base of pectoral fin. 91. 



3. Tchthyodectes sp. ; two vertebral centra, showing lateral pits, side view. 



-Chalk; Burham. Harford Collection (B. M. no. P. 5718). 95. 



4. Tchthyodectes sp. ; five terminal caudal vertebras, left side view. — Chalk; 



Burham. Toulmin Smith Collection (B. M. no. 41691). c, centra; 



/(., haemal arches; v., neural arches. 95. 



5. IclUlt/yodectes sp. (Gladocyclas lewesiensis, Agassiz) ; scale. — Chalk; 



Sussex. Dixon Collection (B. M. no. 25861). c, exposed sector. 96. 



6. Ditto ; scale. — Zone of Holaster subglobosus ; Burham. Toulmin Smith 



Collection (B. M. no. 41712). e., exposed sector. 96. 



7. Ichthyodeetes tenuidens, A. S. "Woodward; head, right side view. — 



Probably from zone of Holaster subglobosus ; Burham. Mrs. Smith's 

 Collection (B. M. no. 49054). co., circumorbital cheek -plate ; d., 

 right dentary (the left crushed below) ; mx., maxilla; pi., palatine; 

 pop., preoperculum ; prf., prefrontal; scl., ossified sclerotic. 98. 



8. Portheus mantelli, Newton ; the type specimen, showing the imperfect 



left premaxilla (jmix.) and maxilla (mx.), outer aspect, with the 

 counterpart half of the same premaxilla (8 a). — Probably from a 

 Turonian zone; Lewes. Mantell Collection (B. M. nos. 4066-67). 101. 



9. Portheus mantelli, Newton (?) ; centrum of caudal vertebra, side view 



showing lateral pits. — Chalk; " Gravesend." Bowerbank Collection 

 (B. M. no. 39065). It., base of hsemal arch; n., base of neural arch. 102. 



All the figures of the natural size. 



