﻿72 ME. T. F. SIBLT ON THE FATJNAL SUCCESSION IN THE [Feb. I 908, 



nature of my specimens does not justify the creation of a new species. 

 This form is closely similar to Koninckophyllum sp., figured by 

 James Thomson in Proc. Phil. Soc. Glasgow, vol. xiv (1882-8;3) pi. xi, 

 figs. 5 & 6. 



Lonsdalia. 



LoNSDALiA DUPLicATA (Martin). (PI. I, fig. 5.) 



Habit of growth and form. — Compound, dendroid, the 

 corallites being cylindrical, very unequal in diameter, and loosely 

 aggregated. 



E pi thee a. — Thick, concentrically rugose, and distinctly costate. 



In a horizontal section of a corallite : — The central area is 

 generally loose and rather irregular in structure, the radial lamellae 

 being few in number and often incompletely developed. The mesial 

 plate is usually well-developed. 



The primary septa, which extend inwards to the boundary of the 

 central area, are thickened and very prominent within the inner 

 wall. They usually terminate a very short distance outside the 

 inner wall, and very rarely reach the outer wall. Secondary septa 

 are, as a rule, either absent or of very rudimentary development. 

 The inner wall, produced by a thickening of the dissepiments, is 

 very conspicuous. 



The external area, radiated by the septa and containing dissepi- 

 ments, is extremely narrow aud inconstant. The broad peripheral 

 area, composed of very large vesicles, has a width approximately 

 equal to half the radius of the corallite. 



Discussion. — William Martin's original description and figure^ 

 of Lonsdalia duplicata furnish no details of the internal structure 

 of the coral ; and although ^['Coy ^ gave a detailed description of 

 the species, based on Derbyshire specimens, his description is not 

 accompanied by a figure. Specimens collected by me in the 

 Midland area agree in external form with the original specimen 

 of Lonsdalia duplicata, as represented in Martin's work, and also 

 agree completely with M'Coy's description of the species. I have, 

 therefore, thought it advisable to redescribe the species, at the 

 same time figuring a typical specimen. 



The coral figured as Lonsdalia duplicata by Thomson & JS'ichol- 

 son,^ is in fact widely difi'erent from that species, as shown by the 

 following characters of a horizontal section : — (1) A sharply- 

 bounded central area, in which radial lamellge are generally 

 numerous and regular. (2) Thin, flexuous primary septa, and a 

 regularly-developed secondary series. (3) A comparatively-wide 

 external area, radiated by the septa ; and a poorly-defined inner 

 wall. (4) A peripheral area composed of comparatively - small 

 vesicles. 



Horizon. — Lonsdalia duplicata occurs in the upper part of D^ 



^ ' Petrificata Derbiensia ' 1809, pi. xxx. 



2 ' Brit. Pal. Foss.' 18.55, p. 105. 



3 Ann. & Mag. Nat. Hist. ser. 4, vol. xvii (1876) pi. xvi, figs. 2 & 2a. 



