574 J. W. KIEKBT ON MAEINE POSSILS IN THE 



Pig. 4 represents a section of this bed, explanatory (with the 

 details that follow) of the distribution of the above fossils. 



Commencing at the base, the grey shale and sandstone band a 

 contains large Stigmarian roots and rootlets, SphenopteAs affinis 

 and other plants, the scales and bones of small Ganoid fishes, teeth 

 of Diplodus, and carapace -valves of Leperditia OJceni, var., and 

 Beyrichia subarcuata. This deposit evidently indicates an area on 

 which grew large trees, the roots of which only remain. 



The lower leaf of limestone, 6, is a foot thick, and very siliceous 

 below. The inferior portion of it is full of fragments of stems and 

 carbonized wood, aU apparently drifted, and many incrusted with 

 Bpirorbis. A few specimens of Myalina modioliformis are seen here, 

 and occasionally large teeth of Bhizodus Hihherti, 



In the upper portion of the same leaf of limestone the Myalina 

 becomes more numerous, and the fragments of wood less so than 

 below. 



The nine inches of dark grey shale, c, that separates the limestone 

 into two leaves contains many individuals of Leperditia OJceni, var., 

 and Beyrichia subarcuata, var., with a few of Myalina modioliformis, 

 and the remains of Lepidophyllum and other plants. 



The lower half of the limestone, d, is filled with Myalina modioli- 

 formis. Along with it are found Nucula lineata, Littorina scotobur- 

 digalensis, Leperditia Okeni, and Spirorbis. Many of the Myalince 

 are in single valves, and still more of them are fragments, worn and 

 rounded, the thick umbonal bits being very common. The Spirorbes 

 are found both attached to the Myalina and free. 



Higher, but not including the top portion, the Myalina is 

 associated with Schizodus Salteri and Sanguinolites sp., Littorina 

 scotoburdigalensis, Macrocheilus striatulus, Leperditia Okeni, and 

 Spirorbis in abundance. The shells of the Sanguinolites form a thin 

 layer in this part of the bed. The other bivalves occur mainly as 

 single valves or as fragments, though not so much worn as im- 

 mediately below. Spirorbis incrusts all these shells, the interiors 

 of the ScJiizodus being often beautifully covered with it. 



In the top two inches of the limestone there are none of the 

 Myalina^ Schizodus Salteri taking its place as the prevailing species. 

 "With it occur Orthoceras sp., MurcJiisonia quadricarinata, Naticopsis 

 plicistria, Loxonema scalaroidea, Macrocheilus striatidus, Aviculo- 

 pecten granosus, Sanguinolites abdensis, S. subplicatus, Nucula lineata, 

 Lingida mytiloides, Gythere Jonesiana, C. cequalis, Leperditia Okeni, 

 L. Okeni, var., Beyrichia subarcuata, B. sid)arcuata, var., Kirkbya 

 spiralis, Spirorbis globosus, S. helicteres. The valves of the lamel- 

 libranchs are mostly detached, but not much worn, the hinge-teeth 

 being sharp and well preserved in carefully extracted specimens. 



The above details of the distribution of fossils in this bed show 

 changes from an area of tree-growths towards marine conditions 

 of increasing intensity. Other marine beds in the Calciferous 

 Sandstones show pretty much the same sort of progression ; but in 

 many cases the advance towards marine conditions does not reach 

 further than the introduction of MyaUna modioliformis. 



