﻿1G4 BRITISH STROMATOPOROIDS. 



referable to L. canadensis, since the radial pillars are commonly more or less 

 entirely destroyed in undoubted examples of this species. If we were to suppose 

 that radial pillars were really wanting, the specimen would have to be referred to 

 the genus Rosenella, Nich. ; but this reference is negatived by the fact that the 

 upper surfaces of the vesicles, as seen in vertical sections, are quite smooth, and 

 are completely destitute of the tubercles which are present in this situation in all 

 species of the genus Rosenella. 



Distribution. — A single large specimen was collected by Mrs. Robert Gray in 

 the Aldons Limestone (Ordovician) at Aldons, near Girvan. The typical forms of 

 the species are found in the Trenton Limestone of Peterborough and Lake 

 Couchiching in Ontario. The species also occurs in the Ordovician Rocks 

 (" Wassalem Beds ") of Saak in Esthonia. 



Family— STROMATOPORID^E. 



Genus 1. — Stromatopora, Goldfuss (emend.), 1826. 

 (Introduction, p. 91.) 



1. Stromatopora concbntrioa, Goldfuss. PI. Ill, fig. 5 ; PI. XI, figs. 15 — 18 ; PI. 



XX, fig. 10; PI. XXI, figs. 1—3; and 

 PI. XXIV, figs. 9 and 10. 



Stromatopora conoentrica, Goldfuss. Petref. Germ., p. 22, pi. viii, fig. 5, 1826. 

 ? — — Michelin. Iconographie Zoopbytologique, p. 190, 



pi. xlix, fig. 4, 1840—47. 



— — Nicholson. Monogr. Brit. Strom., Introduction, 



p. 2, pi. xi, figs. 15—18, 1886. 



— — Waagen and Wentzel. " Salt Range Fossils," Palae- 



ontologia Indica, No. 7, pi. cxx, figs. 

 4 and 5, and pi. cxxi, 1 a — 1 c, 1887 

 (figured, from European specimens, 

 but not described). 



— — Wentzel. Ueber fossile Hydrocorallinen, " Lotos," 



Neue Polge, Bd. ix, Taf. ii, figs. 4 and 

 5, and Taf. iii, figs. 1 and 2 (figures 

 only), 1889. 



The ccenosteum in this species is massive, spheroidal, cylindrical or bluntly 

 conical, or irregular in form, often attaining a very large size. The base of 

 attachment seems to have been small, and an epithecal membrane does not appear 

 to have been developed. The skeleton always consists of successive " latilaminge," 

 or concentric strata, which are generally 2 to 3 mm. in thickness, and mark 

 periodic intermissions in the process of growth (Plate XX, fig. 10, and Plate 



