Vol. 68.] SUCCESSIOIf IN THE IfOETH-WEST OP ENGLAND. 563 



genus Thysanophyllum,^ and subsequently figured by Thomson.^ 

 It agrees witb the latter author's figure of Tli. minus in most 

 particulars, especially in the fact that one septum is character- 

 istically prolonged into the centre of the tabulate area, and that 

 a few of the septa occasionally extend into the outer vesicular 

 zone. M'Coy's species seems to diff'er from both of Thomson's 

 species, chiefly by the coarser character of the vesicles in the peri- 

 pheral zone. This species appears to represent an early form of 

 Lonsdalia florifonnis. Mr. K. Gr. Carruthers, who has devoted 

 special attention to the ancestry of Lonsdalia, has demonstrated 

 that L. floriformis passes through a very distinct Thysanojpliyllum 

 stage in early life : this would appear to show that Lonsdalia 

 has descended, not through. Libunophyllum, as sometimes suggested, 

 but through Thysanopliyllum. This view seems to be further 

 strengthened by the existence of the form intermediate between 

 Lonsdalia and TJiysanopJiyllum, already mentioned as occurring 

 with Stenophragma in Ravenstonedale. 



Horizon and localities. — This species is limited to an 

 horizon near the summit of the Athyris-glahristria Zone, in the 

 Eastern Districts of the North- Western Province. It is found at 

 many places between the E-iver Eaniont and the Dent Fault, in the 

 type-districts ; in Hall-Head Quarries and in the cuttings for the 

 Underbarrow and Brigsteer roads, Kendal District ; above Broad 

 Oak in the Grange District; and in Dobby-Hole Sike to the south 

 of Homan Fell. 



DiPHTPHYLLrM aff. LATESEPTATUM M'Coy. (PI, L, figs. 8 « & 8 6.) 



This form differs from D. lateseptatum of M'Coy in the greater 

 breadth of the tabulate area, which extends across four-fifths of 

 the width of the corallite. The tabula are perfectly horizontal 

 throughout the greater portion of their extent, but bend down 

 steeply at their margins, and frequently have the appearance of 

 bifurcating before reaching the peripheral zone, which consists of a 

 double row of very fine vesicles (PI. L, fig. 8 6). 



In transverse sections the oblique lateral margins of the tabulae 

 are intersected, to form sparse interseptal tissue (fig. 8 a). 



Horizon and localities. — Base of the Productus-corrugato- 

 liemispJiericus Zone. Blackstone Point, Arnside District; Tarn 

 Sike, Eavenstonedale District. 



LiTHOSTEOTION (NeMATOPHTLLUM) MINUS M'Coy. 



The form figured by M'Coy in 1849 in the Annals of Natural 

 History (ser. ii, vol. iii, p. 17), and afterwards in his ' Palaeozoic 

 Rocks & Fossils ' 1855, p. 99 & pi. iii 6, fig. 3, was collected from 

 the Kendal District, where it occurs abundantly on the summit of 

 Scout Scar and Kendal Fell. M'Coy gives good figures, and the 

 type-specimens are preserved in the Sedgwick Museum at Cam- 



1 Proc. Roy. Soc Edin. vol. ix (1876) p. 150. 



2 Proc. Phil. Soc. Glasgow, vol. xii (1880) pp. 255-58 & pi. iii, figs. 11-12, 14. 



2s2 



