On the Internal Structures and Classificatory Position of Micrabacia coronula , Goldfuss, sp.

Abstract

Micrabacia coronula, Goldfuss, sp., called Cyclolites by William Smith (1816), is a characteristic fossil of the Upper Greensand, and has been found at Warminster and, according to W. Smith, at Chute Farm and Paddle Hill, near Dunstable, and in the beds at Essen and Le Mans; it is also found in the “Cambridge Greensand.” Bolsche has described a Micrabacia from the Senonian. The external characters of the species have been beautifully delineated by Milne-Edwards and Jules Haime, in their monograph of the British Fossil Corals , and the description of the specimen used as a type is, as might be anticipated, careful and correct. Allowing for variation in some parts, the description permits any specimen to be recognized, specifically, from the appearance of the external structures. It does not appear that these authors made sections of this coral, and as their work was classificatory and not necessarily morphological, they probably did not think it necessary to investigate the internal structures specially. The generic diagnosis of the type was also carefully given by Milne-Edwards and Jules Haime, and the genus Micrabacia was separated from the genus Fungia , Dana, by them. They placed the genus in the family of Aporose Corals called Fungidæ by Dana, and in their own subfamily Funginæ, which includes Fungidæ with perforated walls. The generic and specific diagnoses and the synonymy are given in the ‘Histoire Naturelle des Coralliaires,’ vol. iii. p. 29. After the careful descriptions of these authors had appeared, came the work of M. de