108 PEOP. p. MAETIN DUKCAN Olf THE 



fig. 2, under the name of Stylastrcea plana, Dune, sp., does not 

 correspond with the type of A. plana. It is not that of an 

 Astrocoenian, for its septal arrangement, short costse, thin walls, 

 and intermediate coenenchyma are not characteristic of the genus, 

 and they are not present in any of the Infra-Liassic forms I have 

 described. The figure is unlike a section of any species of Styl- 

 astrcea (see the short costse). 



ASTEOCCENIA COSTATA, UoMs, Op. Clt. p. 21, pi. ix. figS. 15-17. 



This species has all the generic characters of Astrocoenia. Never- 

 theless it has been placed in the genus Stylastrcea, E. de Prom., and 

 it has been stated to be synonymous with >S. sinemuriensis, E. de 

 Erom., in consequence of the presumed resemblance of the published 

 figures of the Erench and "Welsh species. The following statement 

 is made in "A Critical and Comparative Revision of the Madreporaria 

 of the White Lias," &c. (Quart. Journ. Geol. Soc. vol. xl. 1884, 

 p. 370) : — " Any doubt that may exist as to the identity of S. sine- 

 muriensis, E. de Erom., with Astrocoenia costata, Duncan, will be 

 readily removed by comparison of fig. 7 of the former (Martin, Infra- 

 Lias de la Cote d'Or, p. 94, pi. viii. figs. 6, 7) with fig. 16, of "fehe 

 latter species," in Pal. Soc. Corals of the zone of A. angulatus, 

 pi. ix. figs. 15-17. 



Palaeontologists occasionally see difierently, and therefore it is as 

 well to read the descriptions of the forms which are represented in 

 the drawings. It will then be noticed that the figures are not 

 drawn on the same scale, and the calicos which are stated to be 

 identical are not of the same dimensions in nature. The Erench 

 form is double the size of the Yv^elsh. The fiat view of the Stylas- 

 trsean prevents its projecting calice being shown; and this, in nature, 

 is different from the depressed calice of the Astrocoenian. The costae 

 of the two forms, as shown in the figures, are positively different. 

 The septa of the two forms differ in their number and cyclical arrange- 

 ment. The figures, instead of confirming the identity, emphasize 

 the distinctness of the forms, and this is still further proved by an 

 examination of the morphology. 



The thin walls and intermural cellular structure or coenenchyma 

 of Stylastrma are not present in the Astrocoenian. Astrocoenia 

 costata, nobis, is quite distinct from and totally unlike Stylastrcea 

 sinemimensis, E. de Erom. 



AsTEOC(ENiA STJPEEBA, uobis. op. cit. p. 21, pi. ix. figs. 3-5. 



This well-marked Astrocoenian has fine costae, and it is only 

 necessary to remind those palaeontologists who have seen and handled 

 the form in the Museum at Bath, that the artist has chosen for illus- 

 tration a part of the corallum in which the costae do not interdigitate 

 so much as elsewhere. This species is stated, in the critical memoir 

 above cited (p. 370), to be identical with Stylastrcea Martini, E. de 

 Erom. " After an examination of the type specimen of A. super ba," 

 says the author, " I am perfectly satisfied of its identity with the 

 previously described Stylastrcea Martini, E. deErom., to which species 



