﻿LABECHIA CANADENSIS. 163 



the confluence of the radial pillars into a reticulation of sinuous rows, the large 

 size of the axial canals, the presence of curved transverse partitions in the in- 

 terior of the axial canals of the pillars, and the fact that the interstitial tissue is 

 composed of straight horizontal plates, which but rarely become vesicular, and 

 then only to a very limited extent. 



Distribution. — Middle Devonian of Devonshire. The only known specimen is 

 in a red limestone, and is probably from the neighbourhood of Torquay. 



5. Labbchia canadensis, Nick, and Mur. sp (?). PI. XX, fig. 9. 



8tromatocehium canadense, Nicholson and Murie. Journ. Linn. Soc. Zool., vol. 



xiv, p. 223, pi. iii, figs. 9, 10 (1878). 

 Lauechia canadensis. Nicholson. Mon. Brit. Stroinatoporoids, pi. ii, figs. 3—5, 



1886. 

 — — — Ann. and Mag. Nat. Hist., ser. 5, vol. xviii, 



p. 14, pi. ii, fig. 5, 1886. 



Typical American examples of this species have a generally massive ccenosteum, 

 the upper surface of which is not fully known. The skeletal tissue (Plate II, figs. 

 4 and 5) consists of large, comparatively remote, and irregularly developed radial 

 pillars, which are united by a very irregularly developed vesicular interstitial 

 tissue, the cells of which are usually of large size and irregular form, though 

 occasionally of moderate dimensions. The vesicles have their convexities turned 

 upwards, and the radial pillars terminate upwards in pointed extremities. 



This species is distinguished from all the other forms of the genus by its 

 irregular and often remote radial pillars, and by the large size and irregular form 

 of the interstitial cells. The only British specimen which I should feel disposed 

 to identify with L. canadensis is a massive Stromatoporoid collected by Mrs. 

 Robert Gray in the Ordovician limestones of the neighbourhood of Girvan. Un- 

 fortunately this specimen, as, indeed, is usual in all examples of the species which 

 I have examined, is in a highly mineralised condition, and its characters cannot 

 therefore be determined with absolute certainty. Vertical sections (Plate XX, 

 fig. 9) show longitudinal rows of large-sized lenticular vesicles, of very irregular 

 dimensions, and thus closely resemble corresponding sections of typical examples 

 of L. canadensis. The vesicles vary from less than a millimetre to about 3 mm. 

 in their long diameter. On the other hand, though the vesicular tissue is 

 sufficiently well marked, there are only obscure indications of the presence of 

 the radial pillars, which must have existed if the species is rightly identified. 

 Upon the whole, however, I have little doubt but that this specimen is really 



