CORALS FROM THE GREAT OOLITE. 123 



specimen here figured is much weather worn, and has lost its epitheca as well as the edge 

 of the trabicvdar septa, which assmiie the appearance of raoniliform costal striae. The 

 scla?renchymatous nodides that constitute these styliform septal processes or trabicula) are 

 placed nearly at equal distances from each other in the same series and in the adjoining 

 series, so that when they occupy a large surface they appear to be arranged in a very 

 regular manner according to three straight lines : one almost vertical, and the two others 

 oblique and crossing each other at right angles, (fig. 6i.) Calices quite superficial ; the fossula 

 are not deep, but are well defined and placed at a considerable distance from each other. 

 The septo-costal radia are numerous (about thirty or forty), very thin, broad, especially those 

 that are placed perpendicularly to the edge of the corallum, almost equal in size, rather 

 closely set, completely confluent, and formed of a series of nodular styliform processes as 

 already stated. The specimen which is figured in this work, and belongs to Mr. Walton's 

 rich collection, is about one inch high and two broad ; the corallites are about one and a 

 half lines in diameter. 



This fossil is found in the Great Oohte at Bradford Hills, and at Dunkerton ; Prof 

 M'Coy states its having been met with at Minchinhampton. 



Lamouroux, who established the genus Microsolena had very false ideas of its structure 

 and zoological affinities. He supposed that the trabiculae which constitute the septa were 

 tubes bored in a common mass. M. Michelin recognised the resemblance between 

 Microsolena and Pontes, but placed the former in the genus Alveopora of Messrs. Quoy 

 and Gaimard, from which it differs much. An attentive examination of various specimens 

 of the Microsolena jjorosa, of Lamouroux, found near Caen, and of some other species, 

 has enabled us to ascertain that the genus Microsolena must not be discarded but placed in 

 the Family of the Poritida, near the genus Coscinarcea, from which it differs principally 

 by the existence of a common epitheca, and by the septal trabiculae being placed further 

 apart. We also refer to this generical type some species of a somewhat dencboid 

 form that M. Michelin placed in the genus Alveopora, and have been considered by 

 M. D'Orbigny as constituting two new genera : Bendrarcea and Baciylarcea} 

 M. D'Orbigny characterises the first of these divisions as JDcyidriform Microsolena, 

 and the second as Dendriform S^nastraa, but we have ascertained that the typical 

 species of both present the same structure as Microsolena, and the insignificant 

 differences which exist between massive, gibbose, or subdendroid forms^ are not in 

 our opinion of sufficient zoological value to be employed as characteristic of generical 

 divisions. 



Microsolena regularis resembles very much, by its general form, Microsolena porosa," 

 but differs from it essentially by its septa being much more numerous and closer set. 



1 Note sur des Pol. Foss., p. 1 1. 



2 Lamouroux, Exp. meth., tab. Ixxiv., figs. 24, 2J, 2G. 



