252 FOSSIL FISHES OF THE ENGLISH CHALK. 



of the marginal teeth of the splenial resemble those ascribed to the dentary, 

 though their central cone is relatively smaller and less elevated ; but a few of 

 these teeth just within the coronoid elevation tend to lose the cingulum on the 

 outer face (fig. ob), and extend downwards and forwards on their inner face, while 

 their apex is inclined forwards (fig. 5«). The small intermediate teeth are 

 especially irregular, largest and most distinctly ovoid along the inner margin of 

 the splenial, most definitely mammillated in the two rows external to the principal 

 row. 



Acrotemnus faba, Agassiz (p. 169). 



An associated set of teeth of an allied species, A. splendens, from the Upper 

 Senonian of Harmignies, near Mons, Belgium, has been described by M. Leriche, 

 Bull. Soc. Beige Geol., vol. xxv (1911), Proc. Verb., p. 162, pi. A. The anterior 

 teeth are hooked and prehensile, resembling the specimen shown in PI. XXXV, 

 fig. 8. 



The Jurassic Pycnodont teeth most closely similar to the molars of Acrotemnus 

 are those of Mesturus (A. S. Woodward, Ann. Mag. Nat, Hist. [0], vol. xvii, 1890, 

 p. 1, pis. i — iii). 



Notidanus pectinatus, Agassiz. 



1843. Notidanus pectinatus, L. Agassiz, Poiss. Foss., vol. iii, p. 221, pi. xxxvi, fig. 3. 



This name was given to a tooth, originally in the Mantell Collection, which 

 differed from V. microdon (see p. 222) in having distinct denticles instead of mere 

 serrations at the base of the principal cusp anteriorly. No other specimen has 

 been discovered. 



SUMMAUY AND CONCLUSION. 



So large a proportion of the fishes from the English Chalk are still known only 

 by fragments that this Monograph is necessarily disappointing. It is merely a 

 pioneer work, which shows how much remains to be discovered concerning even 

 some of the commonest fossils. It is, however, interesting in at least three respects, 

 and leads to results which are not without value. The detailed descriptions of the 

 cranial osteology of the bony fishes indicate closer resemblances between the 

 Cretaceous genera and their existing representatives than have hitherto been 

 suspected. The highly specialised skull of Hoplopteryx, for example, is shown to 

 have remained unchanged from the Cretaceous period to the present day. At the 



