CRETACEOUS EN ALIOS AURS. 455 



SUPPLEMENT NO. I. 

 CRETACEOUS ENALIOSAURS. 



Ord^r—SJUROPTFEYGIJ, Owen* 

 Genus — Polyptychodon, Owen. 



POLYPTYCHODON INTERRUPTUS, Owen. ■» 



In Chapter III, on Fossil Reptilia of tlie Chalk Formations, pp. 209 — 21:2, 

 certain dental and osteological charanters of a large extinct Saurian were described 

 and figured, confirmatory of the distinct generic form of reptile, for which had 

 been proposed the name Pol^pfi/chodon,\ having reference to the numerous longi- 

 tudinal ridges and grooves, giving a minutely folded surface to the enamel cover- 

 ing the crown of the tooth. In my ' Report on British Fossil Reptiles,' the genus 

 was referred to the ' Sauria incertse sedis,' no other parts save the teeth being 

 then (1841) known. A ie\w years later a portion of jaw was discovered in the 

 Lower Chalk of Kent, showing that the teeth were implanted in distinct sockets, 

 as in the CrocodUia. This specimen I described and figured in the work of my 

 friend, Mr. Dixon, entitled ' The Geology and Fossils of the Tertiary and Cre- 

 taceous Formations of Sussex.';}: 



Some large fossil bones from a Green-sand quarry near Hythe, Kent, described 

 in the above-cited chapter, p. 201, as probably belonging to Polyptychodon^ 

 showed that " the pubis and ischium approached somewhat to the Plesiosaurian 

 type." 



Cranium and Teeth (PI. 14, figs. 1 — 3. 



I have lately been favoured by Mr. George Cubitt with the inspection of part 

 of the cranium, including portions of jaws with teeth, of Polyptychodon 

 interri/ptus, discovered in cutting a railway tunnel through the Chalk formations 

 near Frome, Somersetshire, which gives further evidence of the Plesiosauroid 

 affinities of the genus, in the presence of a large oblique "foramen parietale " 

 between the frontal and parietal bones {Enaliosauria, PI. 14, fig. 1, v). 



* 'Eeport of the British Association,' 1859, p. 153. 



t This genus was established, on the characters of detached teeth from the Chalk, in the author's 

 " Report on British Fossil Reptiles," ' Traus. of the British Association,' 1841, p. 15G. 

 X 4to, 1848, tab. xx.\Tiii, fig. 3. 



