54 WEALDEN AND PURBECK FOSSIL FISHES. 



much the larger. The smooth complete scales on the lower portion of the flank, 

 becoming reduced backwards, are especially well seen in the type specimen (PI. 

 XII, fig. 3), and their stout inner rib is still clearer in the second specimen (fig. 4). 

 The dagger-shaped scales of the upper slime-canal are also distinct. The course 

 of the lateral line is obscure in the abdominal region, but it is marked by a row of 

 short tubular calcifications on the tail (fig. :3, /./.). A small smooth rhombic scale 

 occurs on the upper extremity of the caudal lobe. 



Horizon mill Locality. — Middle Purbeck Beds: Teffont, Wiltshire. 



Genus EOMESODON, novum. 



Generic Characters. — Profile of head especially steep and abdominal region of 

 trunk much deepened; the caudal region relatively small. Head and opercular 

 bones more or less coarsely granulated ; jaws and teeth as in Mesodon, but with 

 not less than three outer series of splenial teeth. Fins as in Mesodon. Scales 

 complete over the whole of the trunk in advance of the median fins, not much 

 deepened ; ornamented with more or less coarse granulations. 



Type Species. — Eomesodon liassicus {Pycnodus liassicus, Egerton, Figs, and 

 Descript. Brit. Organic Remains, dec. viii — Mem. Geol. Surv., 1855 — no. 10) from 

 the Lower Lias probably of Barrow-on-Soar, Leicestershire,, and other English 

 localities. 



Remarks. — The species referable to this genus have hitherto been included in 

 Mesodon, but they form a group which is well distinguished by the deepening of 

 the large abdominal region and the completeness of the abdominal squamation. 

 The earliest species is Eomesodon hoeferi,* from the Upper Trias of Hallein, 

 Salzburg, Austria. Next is the type species from the Lower Lias, and then follow 

 the other Jurassic species, Eomesodon rugulosus* E. granulatus? E. gibbosusf and 

 E. barnesi, besides an uncertain number of species which are known only by the 

 dentil ion. 



The dorsal elevation of the anterior part of the trunk in the type specimen of 

 Eomesodon liassicus is not well shown in Egerton's original figure of this fossil. 

 It, is therefore drawn again in the accompanying Text-fig. 21, which indicates some 

 of the principal features of the genus and species. The skull is evidently that of a 



1 Mesodon hoeferi, D. G. Kramberger, Bsitr. Palilont. unci Geol. Oesterr.-Ungarns, vol. xviii 

 (1905), p. 219, pi. xx, fig. 5; pi. xxi, fig. 2. 



2 Pycnodus rugulosus. L. Agassi/,, Poiss. Foss , vol. ii. pt. ii (1839 — 44), p. 194, pi. lxxiia, fig. 23; 

 Mesodon rugulosus, A. S. Woodward, Proe. Geol. Assoc, vol. xii (1892), p. 239, pi. iv, figs. 2—4. 



3 Pycnodus granulatus, Graf zu Minister, Beitr. Petrefakt., pt. vii (1846), p. 44, pi. iii, figs. 11,12; 

 Mesodon granulatus, K. Fricke, Palaeontogr., vol. xxii (1875), p. 359, pi. xviii, pi. xix, figs. 1 — 5. 



1 Mesodon gibbosus, A. Wagner, Abhandl. k. bay. Akad. Wiss , math.-phys. CI., vol. vi (1851), 

 pp. 52, 56, pi. iii, fig. 2 : E. Hennig, Central!)!, f . Min., 1907, p. 366, figs. 4, 5. 



