120 Rev. A. Sedgwick on the Geological Relations and 



11. Mytilus squamosus (S. N.), ovate, acuminate, the laminae of the shell having the appear- 

 ance of scales; length more than an inch. In considerable abundance near Ferry Bridge, but 

 generally in the form of casts. 



12. Pecten. 1. (S. N.) smooth, half an inch in diameter. Abounds at Humbieton, &c. 



2. (S. N.) convex, circular, marked with striae, slightly tuberculated ; about 



the same size as the preceding. Humbieton. 



3. To this list Mr. Phillips has added a circular fluted species two inches and a 



quarter in diameter. 



13. Plagiostoma (?) — Casts of a very small beautifully striated shell, apparently of this genus, 

 occur at Humbieton. 



14. Venus (?) — Casts of a gibbous shell three-quarters of an inch in diameter, resembling this 

 genus, are found at Humbieton*. 



Crinoidea. 



Portions of the columns of one or two species belonging to this family are 

 found in great abundance in the quarries near Humbieton ; they also occur 

 in the cliffs of Tynemouth. These fossils are rarely, if ever, found in the 

 range of the formation to the south of the Tees. Some specimens from Hum- 

 bieton and Tynemouth have been examined by Mr. Miller, and are referred 

 to the Cyathocrinites planus^. 



Coralline Bodies. 



Two reteporesj, mixed with casts and fragments of other coralline masses, 

 abound in the shelly magnesian limestone of Humbieton and other parts of 

 Durham§. The specific w^me^ Jlustracea and virgulacea are adopted from 

 the MS. Catalogue of Mr. Phillips of York ; and the figure of the Retepora 

 virgulaceaW is taken from a specimen kindly lent by that gentleman. Traces 

 of two other corallines^ occur also at Humbieton. 



Vegetable Fossils. 

 The specimens to be enumerated under this head have been already noticed. 



1. Obscure impressions of two species of Fern from the marl-slate of Midderidge**. 



2. Carbonaceous matter obviously derived from vegetable fossils ; from the marl and blue 

 shelly limestone beds of Palterton and Bolsover ff. 



3. Long cylindrical stems (probably of vegetable origin) traversing the top beds of the first 

 section near Nosterficld J J. 



* In the specimens derived from some of the places above mentioned, especially Humbieton 

 quarry, there are more genera and species than have been enumerated, but they are too imperfect 

 for description. Large additions might undoubtedly be made to the list by a more careful exa- 

 mination of these localities. 



t Nat. Hist. Crinoidea^ p. 85. J Plate XII. fig. 6. 8. 



§ These coralline fossils are very rare in all parts of the formation south of the Tees. I found 

 a single specimen of the Retepora Jlustracea in the beds of blue limestone at Nosterfield, near 

 Taufield. 



II Plate XII. fig. 6. If Plate XII. fig. 5. 7. ** See p. 77. ft See p. 81. +♦ See p. 107. 



