118 Rev. A. Sedgwick on the Geological Relations and 



scales appears to agree with the genus Palajothrissum ; but it differs from all (he described 

 species in its form and size, as well as in (he singuLar decoration of its scales. As the fore part 

 is wanting, it is perhaps better to consider it as belonging (o an unascertained genus. For pur. 

 poses of comparison it is, however, not wi(hout its use ; as fragments of the same species have, I 

 believe, been found in the copper-slate. 



5. A fifth species* has also some characters in common with those already described. It is far 

 too imperfect to be ascertained ; but it is hoped that it may hereafter be compared with better 

 specimens of the species, and for this purpose it is figured. The small side figures show the scales 

 magnified. 



6. Another specimen! diifers entirely from all the former, but it is far too imperfect to be 

 referred to any known species or genus. It may hereafter serve the purpose of comparison. 



7. The operculum of a large fish J. From its size, it seems to belong to a species distinct from 

 any of those which havo been figured. 



8. To (his list may be added the fossil fish found at Pallion, and described by Dr. Clanny and 

 Mr. Winch §. The specimen is preserved in the museum of Sunderland, and has been referred 

 to the <fenus Chaitodon : but this cannot be considered as well ascertained till a more elaborate 

 figure of the fossil has been published. 



Another specimen ||, discovered during the passage of this paper through the press, is probably 

 of the same species with the fish above mentioned from Pallion. It has enabled us to restore the 

 anal fin ; and in the structure of the tail it agrees with the other species. 



It was found in the marl-slate near East Thickley. 



Fossil Shells. 



Univalves. — These are much more rare than bivalves. An instance has, however, been 

 noticed^ where they occur in great abundance ; and they are occasionally found in the shelly 

 beds of yellow limestone in the county of Durham, and in the blue shelly beds near Bolsover, 

 &c. &c, 



1. Turbo (?). — Beautiful small casts of a deeply striated shell, apparently of this genus, occur 

 in the pisolitic yellow limestone between Marr and Hickleton. 



2. Casts of a small smooth shell, apparently of the same genus, are rarely found among the 

 fragments of bivalves in the blue limestone of Palterton and Bolsover, in the lower beds of yellow 

 limestone near Conisborough, &c. &c.** 



3. Pleiirototnaria (?). — Beautiful but imperfect casts of univalves, which Mr. Sowerby refers 

 to this genus, were found among the shelly and coralline masses of Humbleton quarry. One of 

 these exhibits five whorls, and is about 1^ inch in length. 



4. Ammonites A cast of one of the chambers of a small Ammonite was found among the 



Humbleton fossils ft- 



5. Serpnla or Dentalium (?). — Traces of small obscure bodies, belonging to one or both of 

 these genera, occur in some shelly beds on the Durham coast south of Black Rocks. Also in the 

 upper beds at Cold Hill near Aberford. 



* Plate X. t Plate XI. + Plate IX. fig. 3. 



§ See p. 78, note. || Plate XII. fig. 1. H See p. 110. 



** This is probably the same species with the following : — Turbo (?) Spires 4, smooth, length 

 under i of an inch; Hawthorn Hive. (M.S. Catalogue of fossils by Mr. J. Phillips of York.) 



ft To this list may be added five species of Melaniai (?) less than half an inch long, with eight 

 whorls; Ilawdiorn Ilive. (M.S. Catalogue by Mr. J. Phillips.) 



