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A NEW SPECIES OF EDESTUS. 



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the divisions between the roots of the three anterior teeth are 

 well marked by lines of calcite. In each tooth the root is much 

 shorter than is usual in Eclestus, scarcely extending backwards 

 beyond the hinder production of the base of the crown. As shown 

 by the foremost tooth (figs. 2 & 3), the anterior margin of the root 

 slopes downwards and backwards, and is compressed to an edge 

 nearly as sharp as that of the crown. Its truncated lower face 

 (fig. 2) is excavated into a triangular hollow, so that the lower 

 face of the arch of clasping teeth is impressed by a wide longi- 

 tudinal groove, of which the shape and depth are well seen in cross- 

 section (fig. 4). Sections prove that both root and crown are solid, 

 consisting of the usual vascular dentine of rather open texture. 



Irregularly scattered over the shale below the arch of Eclestus 

 -are the more or less broken remains of comparatively small Orodont 

 teeth (o), of the form commonly described as Gampodus or Agctssiz- 

 odus. Some of these teeth are much extended laterally, with a low 

 central cusp (PI. I, fig. 8) ; while others appear to have had little 

 lateral extension, but a relatively-large and elevated central cusp 

 (figs. 9 & 10). The longitudinal ridge on the summit of the crown 

 and all the vertical buttresses on its outer and inner face are sharp 

 .and simply serrated; the superficial gano-dentine is otherwise 

 smooth. The serrated buttress of the central cusp is especially 

 conspicuous on its outer face ; but both this and the lateral but- 

 tresses, which are widely spaced in from one to four pairs, are much 

 more prominent on the outer than on the inner face. The com- 

 pressed root is of very open texture, and seems to be inclined 

 -slightly inwards. 



The fossil itself affords no definite proof that the Orodont teeth 

 thus described belong to the same jaw as the Eclestus, and their 

 very small size seems at first to make their connexion improbable. 

 Teeth of the same type, however, have already been found in 

 association with Eclestus mints 1 ; and one jaw of Gampodus has 

 been described, in which a single arched series of high-crowned 

 symphysial teeth is relatively enormous. 3 Moreover, it will be 

 noticed that in the new fossil from Yorkshire there is no difficulty 

 in regarding the teeth of the Eclestus type as an extreme modifi- 

 cation of those of the Gampodus type which occur with them. In 

 the new Eclestus the central cusp of Gampodus has become exces- 

 sively enlarged and laterally compressed, while the lateral extensions 

 of the tooth are reduced and attenuated, and their sharp crest is 

 represented merely by a faint longitudinal ridge. The irregular 

 basal plications or flutings in the Eclestus are the last remnants 

 of the anterior (outer) lateral buttresses in Gampodus. The first 

 approach, indeed, towards this extreme modification occurs in the 

 symphysial teeth of the typical jaw of Gampodus (Agassi zodus) 

 itself, as shown in the accompanying text-figure (p. 4). Here the 



1 O. P. Hay, Proc U.S. Nat. Mus. vol. xlii (1912) p. 36. 



2 C. R. Eastman, ' On the Nature of Eclestus & Related Forms ' Bull. Mus. 

 •Comp. Zool. Harvard Coll. vol. xxxix (1902) pp. 55-77 & pis. i- iv. 



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