ON REMAINS OF HVPSODON ETC. PROM BRITISH CRETACEOUS STRATA. 505 



25. On the Remains of Hypsodon, Portheus, and Iciiimyodectes 

 from British Cretaceous Strata, with Descriptions of new 

 Species. By E. Tttlley Newton, Esq., E.G.S., of H.M. Geo- 

 logical Survey. (Head. June 6, 1877.) 



[Plate XXIL] 



Dr. Mantell in the year 1822, in his ■ Geology of Sussex,' described 

 and figured certain fossil bones, obtained from the Upper Chalk near 

 Lewes, as the parts of an unknown fish (p. 241, pi. 42). These 

 remains, which it appears were all obtained from one block of chalk, 

 consisted of an upper jaw with teeth, including the maxilla and 

 praemaxilla, with a vertebra and an indeterminable bone. The 

 maxilla, which is there referred to as a lower jaw, is said to " con- 

 tain twelve smooth pointed teeth. These are slightly convex, very 

 brittle, and possess a glossy surface. The three anterior ones are 

 gently curved ; their fangs are hollow, and placed in sockets that 

 extend almost to the base of the jaw. The nine posterior teeth are 

 of a lanceolate form, and probably destitute of fangs, appearing as 

 if attached to the j;iw by anchylosis." 



The appearances which led Dr. Mantell to think the posterior 

 teeth differed from the anterior ones, must, I think, have been due to 

 the condition of the specimen, the teeth of which are somewhat 

 obscured by the matrix ; for, after a comparison with other speci- 

 mens, I see no good reason for thinking that the teeth of this jaw 

 differ otherwise than in size. 



The praemaxilla, which has the remains of " five tusks or de- 

 fences," is broken away from the maxilla. 



Prof. Agassiz, in the year 1843 (' Poissons Fossiles '), without 

 definitely characterizing his genus Hypsodon, alludes to Dr. MantelFs 

 description, and then proceeds to describe the fossil from the Chalk 

 of Lewes, which he calls Hypsodon leiuesiensis (vol. v, p. 99, pi. 25 a. 

 fig. 2). This specimen consists of a large left mandible imbedded 

 in a block of chalk, with what appear, from their position, to 

 be portions of the right mandible, maxilla, and praemaxilla. The 

 mandible is alluded to as being " very thick, with twelve large pro- 

 minent teeth, placed somewhat apart, the anterior ones being nearer 

 together than the hinder ones. The upper jaw has large teeth in 

 front, which appear to be implanted in the intermaxillaries, and 

 form several rows at the end of the jaw." 



A portion of a cranium is next described (pi. 25 a. fig. 1) ; and 

 this Prof. Agassiz thought might belong to the same individual as 

 the previous specimen, being from the same locality. There is a 

 quadrate bone (pi. 25 6. fig. 4), and several other bones, upon the 

 same block. Part of a lower jaw is then alluded to and figured 



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