Reports and Proceedings — Geological Society of London. 137 



•the quartzite. The overthriistinpj force appears to have come from 

 a direction somewhat east of north. 



The igneous rocks are dealt with in two groups : those older 

 and those newer than the earth-movement. To the former belong 

 granite, serpentine, and its associates, and basaltic dykes. In eacli 

 area where they occur the serpentines are associated with masses 

 of a peculiar purple limestone not known elsewhere ; they also 

 contain bands of ophicalcite, and schistose structures are common 

 in the rocks. The later dykes belong to an acid and a basic set ; 

 the latter show some evidence of a minor movement, such as faulting 

 and a little shearing. The acid dykes are microgranites, granophyres, 

 and quartz-porphyries. In some cases the dykes are composite, 

 the acid material being the older and the basic the later constituent. 

 As a rule, the basic material invades the edge of the dyke ; but 

 in one case it has invaded the joints and cracks and caught up 

 fragments of the acid rock. 



3. "The Formation of Dendrites." By A. Octavius Watkins, 

 A.K.S.M., F.G.S. 



If two plane-surfaces be separated by a film of suitable plastic 

 material, and one surface be rotated slowly on the other through a 

 small arc, the plastic material collects into branching forms similar 

 to the structure of dendrites. The dendritic form starts from the 

 part farthest from the axis, and the flow of material is from the 

 smaller to the larger branches, the smaller uniting to form 

 the larger. The author explains dendritic structure by the 

 formation of a fissure in rock which becomes filled with a thin film 

 of dendritic material ; if the fissure is slowly widened, the dendrite 

 starts where the widening commences, coinciding dendrites being- 

 formed on each wall. This theory is in accordance with many of 

 the characters of dendrites, such as their method of occurrence, the 

 nature of the material, and their uniformity in thickness. 



II.— January 24th, 1900.— W. Whitaker, B.A., F.K.S., President, 

 in the Chair. The following communications were read : — 



1. " Fossils in the University Museum, Oxford. 11. On two New 

 Genera and Species of Crinoidea." By W. J. Sollas, M.A., D.Sc, 

 LL.D., F.E.S., V.P.G.S., Professor of Geology in the University 

 of Oxford. 



The first genus and species are founded on two calyces in the 

 University Collection and three in the British Museum ; all the 

 specimens come Irom the Carboniferous Limestone. The arms and 

 stem are at present unknown. The genus in general character and 

 structure recalls Flatycrinus, but the incorporation of the costal 

 and distichal plates in the calyx aff'ords a very obvious distinction. 

 The analysis of the calyx, however, suggests the Melocrinida3, from 

 the members of which it is chiefly distinguished by the comparatively 

 small size of the costal and distichal plates. The new genus is a 

 truly annectant form uniting the Melocrinidaa and the Platycrinida3, 

 and may be indifferently associated with either. 



