ENCHODUS. 55 



original of fig. 1 {plo.), where they are shown to be opposed to the hinder end of 

 the short dorsal fin {do.). The latter is triangular in shape, with about twelve rays, 

 of which the length of the foremost and longest is less than the depth of the trunk 

 at its insertion. Its five anterior rays are especially stout, and ornamented in front 

 with longitudinal rows of fine tubercles ; but all are articulated distally. Some of 

 the supports of the anal fin in B. M. no. 43388 indicate that it must have been com- 

 paratively small and remote ; while remains of the caudal fin both in this and the 

 type specimen show that it was relatively stout and almost certainly forked. 



No traces of scales have hitherto been observed ; but there is a longitudinal 

 series of four or five overlapping dermal scutes on each side of the caudal pedicle 

 just in front of the caudal fin. These are seen both in the type specimen and in 

 B. M. no. 43388, but are too imperfect for description. 



Horizons and Localities. — Zones of Holasfer suhglohosits to Terehyatidina 

 gracilis : neighliourhood of Lewes, Sussex. Zone of Holaster suhglobosus : 

 Burham, Hailing, and Dover, Kent ; Glynde, Sussex. Zone of Terehratulina 

 gracilis or Uhipichonella cuvieri : Burham. Zone of Micraster coranguiniim : 

 Gravesend, Kent. 



Gemis ENCHODUS, Agassiz. 



Enchodus, L. Agassiz, Poiss. Foss., Feuill. 1835, p. 55, aud vol. v, pt. i, 1844, p. 64. 



Isodus, J. J. Heckel, in Eussegger's Keisen, vol. ii, pt. iii, 1849, p. 342. 



Phasganodus, J. Leidy, Proc. Acad. Nat. Sci. Pliilad., 1857, p. 167. 



Ischyrocephalus, W. von der Marct, Zeitschr. deutsch. geol. Ges., vol. x, 1858, p. 248. 



(?) Tetheodus, E. D. Cope, Bull. U.S. Geol. Surv. Territ., no. 2, 1874, p. 43. 



Solenodon, D. G. Kramberger (non Brandt, 1833), Jalirb. k.-k. geol. Eeichsanst., vol. xxxi, 1881, 



p. 373. 

 Holcodon, D. G. Kramberger, Ead Jugoslav. Akad., vol. Ixxii, 1885, p. 18. 

 Euryguathus, J. W. Davis, Trans. Roy. Dublin Soc. [2], vol. iii, 1887, p. 601. 



Generic Characters. — Trunk elongate-fusiform, l}oth this and the head laterally 

 compressed. Cranial roof exhibiting a deep median longitudinal depression, its 

 lateral and occipital margins ornamented, like the other external bones, with ridges 

 and tubercles of ganoine. Mandible a little prominent, provided with an inner 

 widely-spaced series of large slender teeth, the largest in front, also a marginal 

 series of minute teeth, all nearly or completely solid ; premaxilla in the form of a 

 vertical lamina, deepest in front, tapering behind, and with a single spaced series 

 of small teeth ; maxilla long and slender, either finely toothed or toothless at the 

 oral border ; palatine thickened and tumid, with only one large tooth fixed at its 

 anterior end ; ectopterygoid robust, with a single spaced series of large slender 

 teeth, gradually diminishing in size Ijackwards ; no teeth barbed. Preoperculum 



