A. R. Horwood — Upper Trias of Leicestershire. 109 



Ilmenite, in allotriomorphic grains and rhombohedra strongly altered 

 to leucoxene, up to "22 inch in size (usually smaller), present in small 

 amount only. 



Plagioclase, in laths from "01 to "02 inch long by "002 inch wide 

 xisually, often much decomposed, well distributed but subordinate in 

 quantity to augite. 



Apatite, in very small prisms not exceeding "003 inch long, and 

 verj" scarce. 



The order of crystallization seems to have been apatite, plagioclase, 

 ilmenite, enstatite (represented bj' bastite), olivine (represented by 

 serpentine), and lastly augite. 



Two varieties of the rock were distinguished : (1) the normal 

 rock, forming the bulk of the intrusion, in which felspar though 

 a constant constituent is not present in large amounts; (2) a more 

 felspathic variety, lighter and greener in colour, occurring at the 

 margins, top and bottom, of the intrusion. It may be suggested that 

 it is the result of differentiation by fractional crystallization, the 

 felspar being the first essential mineral which crystallized in 

 the rock. 



In microscopical structure the normal rock is more of a picrite than 

 a dolerite, especially in the dominant role played by olivine in the 

 crystallization of the rock. This interpretation is confirmed by the 

 partial analyses of two specimens which yielded 45*07 and 45'4 

 per cent of Si O3 respectively. On the other hand, there is certainly 

 more felspar in the normal rock than in the most typical picrites, 

 though there is hardly enough for a dolerite, even in the felspathic 

 variety. Augite picrites and olivine dolerites are alike hitherto 

 unrecorded from this district. The nearest outcrops of such basic 

 rocks are the hornblende picrites of the Lleyn Peninsula and of 

 Anglesey. 



VII.— The Uppee, Trias op Leicestekshire. 

 By A. E. Horwood. 



{Continued from p. 86.) 



3. Stratigraphy {continued). 



rilHE Dane Hill Sandstone Group, as we propose to distinguish the 

 JL higher of the two series of Upper Keuper sandstones, since it is 

 well developed in the neighbourhood of the Dane Hills at Leicester, is 

 well exposed in a little quarry at Ashleigh House. Here the highest 

 part of the series is seen, with thin beds of flaggy marl and calcareous 

 White or Green Marl, overlying a series of thick-bedded, current- 

 bedded sandstones, of white colour, loose and friable, but hardening 

 on exposure. The section has been described by Browne (1893), but 

 at present is exposed to show a better sequence (see next page). 



On account of the prevalence of JEstJieria in the marly beds 

 and Acrodus in the sandstones they may be distinguished as 

 Estheria Marls and Acrodus Beds, and the beds below the last as the 

 Annelid Bed. 



