20 FOSSIL REPTILIA OF THE 



Orver—SAUROPTERYGIA, Owen* 

 Genus — Polyptychodon, Owen. 



PoLYPTYCHODON INTERRUPTUS, Owen. 



In the ' Monograph of the Fossil Reptilia of the Chalk Formations,' p. 200,t 

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

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

 been proposed the name Polyptychodon,% 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 few 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 Crocodilia. 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 ' Monograph on the Fossil Reptilia of the Cretaceous Forma- 

 tion/|| as probably belonging to Polyptychodon, showed that "the pubis and 

 ischium approached somewhat to the Plesiosaurian type."^[ 



Cranium and Teeth (Tab. IV, 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 

 interruptus, discovered in cutting a railway tunnel through the Chalk formations 

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



* Report of the British Association, 1859, p. 153. 

 t Volume of the Paloeontographical Society, 4to, for 1851. 



X This genus was established, on the characters of detached teeth from the Chalk, in the author's 

 "Report on British Fossil Reptiles," 'Trans, of the British Association,' 1841, p. 156. 

 § 4to, 1S4S, tab. xxxviii, fig. 3. 

 || Monograph, cit. pp. 201 — 209. 

 1 Ibid., p. 206. 



