196 Dr. G. J. Hincle — Western Australian Fossils. 



a new diagnosis. The genus nearest allied to Plerophijlhim is Ani- 

 sophylhim, 1 Edwards and Haime, founded on a small coral from the 

 Devonian of Tennessee, in which only three prominent septa are 

 developed, and these, according to Prof. Nicholson, 2 are the cardinal 

 and alar septa. It is, besides, uncertain, whether the basal portion 

 of the corallum in this genus is infilled by stereoplasm. 



Plerophylltjm Austkale, Hinde, sp.n. Plate VIIIa. Pigs, la-lf. 



Small conical, straight or curved corals, about 30 mm. in height, 

 and from 10 to 14 mm. in diameter at the summit. The number of 

 septa is usually 26 ; of these 5 are large and prominently developed, 

 and 21 are smaller and subequal ; sometimes there are two or three 

 additional smaller septa. The cardinal septum is- small, with a pro- 

 minent septum on either side (PL VIIIa. Fig. Id), Normally, this 

 cardinal septum is on the dorsal or convex side of the coral ; but in 

 some instances the orientation differs, and this small septum between 

 two larger is situated laterally (Figs, le, If). The counter-septum 

 is large, and between it and the large alar septa there are on either 

 side four or five smaller septa. The septa are but slightly developed 

 at the summit margins of the calice ; lower down the prominent 

 septa extend to about two-thirds of the distance to the centre of the 

 calice ; their interior free margins are distinctly tumid or bulbous 

 (Fig. Id), and by successive additional layers of stereoplasm, they 

 become still more so in the lower portions of the coral, until they 

 meet and fill up the central area completely. The smaller septa 

 vary considerably in size and in relative proportions to the larger. 

 Within the calice they are often slender and extend only about one- 

 third the distance to the centre (Fig. Id) ; at a lower level in other 

 specimens they are relatively much larger (Fig. le), and their free 

 margins become bulbous by layers of stereoplasm, which finally unites 

 them laterally, and they can then only be separately distinguished 

 by their dense median lamellas. The corals are not uniformly filled 

 up at the same level with the stereoplasm, and possibly the spaces 

 left vacant may be of the nature of fossulae (Fig. 1/). The median 

 lamella? of the septa are sometimes curved and wavy ; in the Figures 

 (Id, e, f) they are represented by lighter lines as they appear by 

 reflected light ; in thin sections by transmitted light this central 

 substance is opaque and dense. 



The exterior surface of this species when well preserved is smooth, 

 with delicate concentric epithecal stria? (Fig. 16), but when weathered 

 the median lamina? of the septa are shown as deeply impressed 

 longitudinal lines or furrows (Figs. 1, lc). 



This species appears to be not uncommon, but the forms are all 

 imperfect, and the calices are infilled with a hard matrix, so that the 

 interior structures can only be studied from sections. 



Distribution. — Carboniferous, Gascoyne River ; Irwin River, Little 

 Champion Bay, Victoria District. 



1 British Fossil Corals, Pal. Soc. 1850, p. lxvi. Folyp. foss. des terr. pal. p. 351, 

 pi. i. figs. 2, la. 



2 Manual of Pal. 3rd ed. vol. i. p. 296. 



