APPENDIX. 119 



Feet. Inches. 



Blue clay, sometimes red 5 



Limestone. Main seam or " Three-yards Mine." (Fish-remains. Microconchus.) 9 



Coloured shaly clays about 60 



Coal 1 3 



Coloured clays.^ Tliickness not known. 



Leaia Leidyi, var. Salteriana. PI. I, fig. 21. 



Height of valve, more than .. . ^Linch)^) r «r t- i oi 



° ' ^* ^Proportion 7 : 1/, or 1 : 2JL — 



Length „ less than ... -jV „ j 



Some specimens of Leaia, resembling both L. Leidyi and L. Leidyi, var. WilUam- 

 soniana, in general appearance, but relatively shorter, broader, more strongly ridged, 

 more quadrate, and somewhat more rounded on the ventral and posterior borders, have 

 been placed in my hands by Mr. J. W. Salter, F.G.S., of the Geological Survey of Great 

 Britain. They are from the Lower Carboniferous rocks of Pifeshire, Scotland ; and, on 

 account of their differing (though slightly) from the other two forms, and on account of 

 their distant locality and different geological horizon, 1 shall regard them as belonging to 

 a distinct variety, and give it Mr. Salter's name, to whom I am indebted for the 

 knowledge both of these and very many other palaeozoic Entomostraca. 



These specimens of the variety Salteriana are somewhat numerous in a fine-grained, 

 hard, light-brown, clay-ii'on-stone, from Cottage • Row, Crail, Fife ; and are dispersed 

 through the stone ; about twenty-two are to be seen on five square inches. They are 

 associated, I am informed by Mr. Salter, with Lejndodendroii and Lepidostrobus ; and the 

 stratum in which they occm^ is intercalated between beds full of Brachiopods, together with 

 Myalina and Anthracosia. Mr. Salter says that similar beds occur in the district, 

 containing Amhlypterus and BIdzodus, with Cythere (or Cytheropsis) Scotoburdiyalensis. 

 Por an account of the section of the Carboniferous strata of the Fifeshue coast, see the 

 Rev. T. Brown's Papers in the 'Quart. Journ. Geol. Soc.,' 1859, vol. xv, p. 59, and 

 'Transact. R. Soc. Edinb.,' 1861, xxii, p. 385. 



Habitat of Leaia. — The Anthracomy<B associated with Leaia Leidyi, var. Williamsoniana, 

 are probably evidences of at least a brackish condition of the Avater in which this Crus- 

 tacean existed. 



' In the section of the strata at Manchester, given in the 'Silurian System' (1839), p. 87, instead of 

 "clays" at the base, we have "grit or great red rock, with micaceous marls and Unionies, 81 feet," and 

 a long list of still lower strata. This section, based on that of Prof. Williamson, and corrected by Prof. 

 J. Phillips, has some discrepancies with the older one, and its plan of classification differs from that adopted 

 by Messrs. Williamson and Binney. All the limestones, however, I believe, are now regarded as belonging 

 to the Carboniferous system; and Prof. Williamson's original section very well indicates the exact place of 

 the Entomostraca under notice. Prof. Phillips's account of the fossils from the sections at Ardwiclc 

 (' Sil. Syst.,' p. 88, 89) necessarily deserves attention. 



