E. D. Wellbnrn—Fish Fauna of Millstone Grit. 217 



iu depth. At the base of the nodules there is a layer of cone-in- 

 oone, two to three inches in thickness, at the top three to four 

 inches of hard dense limestone, which breaks with a conchoidal 

 fracture, whilst between these the stone is more impure, there being 

 a certain admixture of arenaceous matter, and here the rock will 

 split into lamiuas of from a third to half an inch in thickness. The 

 majority of the fish remains were found on these slabs, but others, in 

 a more fragmentary condition, occur in the upper layers of the nodules. 



That the nodules were foi'med under marine conditions is proved 

 by the fact that mixed among the fish remains are shells of 

 Goniatites, Orthoceras, Avicidopecten, Posidonomya, etc. In some rare 

 instances plants are found, but only in a very fragmentary and 

 eroded condition, and in the upper portions of the nodules 

 I have in rare instances found corals and crinoids. These taken 

 together point to the fact that the fish-bearing nodules were formed 

 under estuarine conditions. 



I have found similar nodules at Wads worth Moor, Yorkshire, 

 where the late Captain Aitken ^ collected his fish remains, and feel 

 certain that his specimens were obtained from the same horizon as 

 the one at Summit. 



Fish remains have also been found in the D Shales of the Middle 

 Grits at the following localities in Yorkshire, viz., Eccup, near 

 Leeds ; Boulder Clough, Sowerby, and Kilne House Wood, 

 Luddenden, both near Halifax ; and the late Mr. James Spencer, 

 of Halifax, mentions- Elonicliihys Aitkeni, Traq., as occurring in 

 the Rough Rock and the B and C beds of the Middle Grits, but 

 unfortunately he gives no localities. 



The collection is of great interest, both from a geological and 

 a zoological point of view — both as largely increasing our knowledge 

 of a fish fauna in a group of rocks whose yield of fossil fish has 

 hitherto been extremely limited, and zoologically in the fact that 

 one genus and several species are new to science, whilst others are 

 placed on record as obtained from these rocks for the first time. 



Concerning the appended list of genera and species the following 

 facts stand out as worthy of special mention (in addition to those 

 mentioned above), viz. : (1) the occurrence of the genus CUmatius, 

 a fish that has hitherto occurred only in the Lower Old Red 

 Sandstones of Forfarshire; (2) the appearance in the Millstone 

 Grits of the genera Orodiis, Psepliodus, Pristodus, etc., for the 

 first time; and (3) the occurrence of the peculiarly interesting 

 Ichthyodorulites, for which I have felt compelled to institute the 

 new genus Euctenodopsis. 



Remarks on the Fisu Remains. 



Family CLADODONTIDiE. 



Genus CLADODUS, A-ussiz, 1843. 



Cladodus mirabilis, Agassiz, 1843. 



The late Mr. Aitken,-^ of Bacup, found teeth of this genus iu the 



' Trans. Mantliester Gcol. Soc, vol. xiii, p. 36. 



» Proc. Yorks. Geol. and Polyt. Soc, vol. xiii, pt. 4. 



3 Aitken, op. cit. 



