284 MR. K. B. NEWTON OX FOSSILS FROM [Aug. 1 0,04,. 



as occurring in the Sarraatian deposits of the Dardanelles or of 

 its immediate neighbourhood. Among these may be mentioned : — 

 Planorbis cornu, Jlelania cf. Escheri, Melan&psis buccinoidea . var., 

 M. incerta, Unio Delesserti, U. cf. Spratti, etc. 



A freshwater deposit occurs beneath the marine Mactra-limestone 

 at San Stefano, from which Col. English has obtained some excellent 

 specimens of Melanojpsis costata (PL XXIY, fig. 15), associated with 

 fragments of an Unio. This alternation of marine and non-marine 

 conditions in the Sarmatian Series has already been alluded to by 

 Prof. Hcernes 1 in connection with the same locality. Prof. Gaudry 2 

 has recorded the occurrence of Melanopsis costata in the lacustrine 

 Miocene of Attica, which would suggest the contemporary deposition 

 of these two sets of beds. 



Pisces. 



DlPLOMYSTUS MARMOREXSIS, Sp. I10V. (PI. XXIV, fig. 28.) 



The type- and only-known specimen of this new species is 

 preserved for the most part in impression, but exhibits many of its 

 essential features. Its total length to the extremity of the caudal fin 

 must have been originally about oS millimetres, while its maximum 

 depth in the abdominal region would be 12 mm. The length of 

 the head with the opercular apparatus is about 15 mm. The jaws 

 are not observable ; and the large orbit is the only distinct feature 

 in the head. The slender, constricted vertebral centra are shown 

 in longitudinal section, and seem to have been pierced by a 

 persistent remnant of the notochord. There are about twenty-four 

 vertebras in the abdominal region, and fourteen in the caudal region. 

 The ribs are moderately stout, and clearly meet the large ridge- 

 scutes at the ventral border. There are also indications of numerous 

 inter-muscular bones. The small pectoral fins are exhibited ; and 

 one of the pelvic fin-supports shows that the pelvic fins were inserted 

 immediately behind a point opposite the origin of the dorsal fin. 

 The dorsal fin is comparatively small, but comprises at least twelve 

 rays : the distance between its termination and the caudal fin is 

 slightly less than that between its origin and the occiput. The 

 anal fin arises slightly behind the posterior end of the dorsal, and 

 is not more extensive than the latter fin : its rays probably number 

 12. The ventral ridge-scutes, about 20 in the series, are uniform 

 in size, and each is produced behind into a slender point. The 

 dorsal ridge-scutes immediately behind the occiput are only seen in 

 imperfect impressions, which appear to indicate that each was 

 longer than broad. There are no traces of ordinary scales. 



Among known species, Biplomystus marmorensis agrees most 

 closely with D. Jiumilis, from the Eocene Green- River Shales of 

 Wyoming (U.S.A.), aud with D. vectensis, from the Lower Oligocene 

 Osborne Beds of the Isle of Wight. It is essentially identical with 



1 Verbandl. d. k.-k. Geol. Keichsanst. 1875, p. 174. 



2 'Animaux fossils & Geologie de lAttique' 1862, p. 406 & pi. lxii, figs. 7-15. 



