STROMATOPORELLA DAMNONIENSIS. 207 



by its total want of perforated tubercles, and the more complete development of 

 astrorhizal cylinders, pointing to a more massive habit of growth. From 

 8. Selwynii, Mch., it is separated not only by the characters just mentioned, but 

 also by the much finer structure of the skeleton. In the general structure of the 

 skeleton, and more especially in the possession of astrorhizal cylinders, 8. socialis 

 more nearly resembles 8. solitaria, Nich., than it does either of the species just 

 alluded to ; but its skeletal tissue is much finer and closer, while the latter has 

 perforated tubercles. From 8. damnoniensis, Nich., lastly, the present species is 

 at once distinguished by the much greater delicacy of its skeleton. There are no 

 other species of the genus known to me with which 8. socialis could well be 

 confounded. 



The great majority of the specimens of Stromatoporella socialis occur in the 

 " Caunopora-state " (Plate XXVI, fig. 0), the " Caunopora-tubes " showing well 

 marked infundibuliform tabula? and, occasionally, radiating spines or " septa." 

 A few specimens appear to be free from " Caunopora-tubes " (Plate XXVI, fig. 5). 



Distribution. — Very abundant in the pebbles of Devonian Limestone in the 

 Triassic conglomerates of South Devon. It occurs also in the Devonian Limestone 

 of Dartington and at Bishopsteignton. An apparently identical form, with a 

 laminar coenosteum, occurs in the Middle Devonian of the Eifel. 



4. Stromatoporella damnoniensis, Nicholson. PI. XXVII, figs. 8 and 9. 



Stbomatopoeella damnoniensis, Nicholson. Ann. and Mag. Nat. Hist., ser. 5, 



vol. xvii, p. 237, pi. viii, figs. 3 

 and 4, 1886. 



The external characters of this species are imperfectly known ; but the 

 coenosteum appears to be in general massive, and more or less hemispherical in 

 shape, with an epithecate under surface. The upper surface is not known com- 

 pletely, but seems to have been generally gently undulated. 



The concentric lamina? of the coenosteum are gently undulated, and the astro- 

 rhiza? are arranged in vertical systems, each of which is built up round a wall-less 

 axial canal ; so that " mamelons " were almost certainly present. At the same 

 time the astrorhiza? are comparatively small and remote. " Astrorhizal tabula? " 

 are present in the horizontal astrorhizal canals. 



The skeleton-fibre is exceedingly thick, and is minutely tubulated. About 

 six lamina? and five interlaminar spaces occupy the space of 2 mm. measured 

 vertically, the lamina? and intervening spaces being of about equal width as seen 

 in vertical sections (Plate XXVII, fig. 0). The radial pillars are confined to their 



