Vol. 68.] SUCCESSION IN THE NOETH-WEST OF ENGLAND. 5e59 



and unthickened character of the major septa, and the relatively 

 great width of the dissepimental zone. 



Horizon and locality. — The upper portion of the Michelinia 

 Zone. Arnside. 



LOPHOPHYLLTJM TESICITLOSTJM, Sp. nOV. (PI. XLYIII, figS. 5^ & 



5 h.) 



In transverse sections this species is characterized by a distinct 

 and thickened plate and the regular symmetry of the central area. 

 The radial lamellae are few in number, and are composed of the 

 attenuated inner ends of some of the major septa. The concentric 

 intersections are numerous, indicating the closely-set and stronojly- 

 arched character of the tabulse ; these intersections diminish 

 towards the outer part of the median area, where the tabulae 

 flatten out, while at the extreme outer margin next to the dis- 

 sepimental area, stereoplasmic thickening of the tissues takes place 

 (PI. XLVIII, fig. 5 a). 



The external area is broad : it consists of a wide zone of fine 

 closely-set dissepiments, which are radiated by major and minor 

 septa, and a narrow border of rather coarse vesicles not radiated 

 by the septa. The longitudinal section (fig. 5 h) shows these 

 characters clearly. 



This species differs from L. meatliopense by the thickened central 

 plate ; by the more numerous, closely-set tabulae in both the central 

 and the medial zones ; by the broad outer zone of dense dissepi- 

 mental tissue ; and by the outer border of coarse tissue not radiated 

 by the septa. 



Horizon and locality. — Seminida-gregaria Sub-zone. Mea- 

 thop, Arnside District. 



LOPHOPHYLLUM ASHFELLENSE, Sp. UOV. (PI. L, figS. 9 rt & 9 6.) 



Cor a] lu m simple, markedly cornute, tapering rapidly. Surface 

 with tine longitudinal ribs and marked concentric growth-con- 

 strictions. Calyx deep ; central plate projecting slightly above 

 the fioor of the calyx, forming a narrow ridge. A distinct 

 septal fossula is present in the cup, which is marked by a shortened 

 septum and also by the slightly Zaphrentid-like curving of the 

 septa bounding the fossula, which coalesce at their inner margins 

 with contiguous septa. The proximal end bifurcates to form broad 

 root-like processes, which in all specimens collected have grown 

 round the shell of a brachiopod, a bryozoan, or a coral. The 

 largest specimen met with measures over 11 cm. in length, and its 

 diameter across the cup is 4*5 centimetres. 



Transverse section (fig. 9 a). — The columella is very thin and 

 lath-like. In the tinai growth-stages it may appear isolated in the 

 centre of the tabulate area, but lower down it is usually in direct 

 connexion with botli cardinal and counter major septa, giving a 

 general bilateral symmetry to cross-sections ; it is surrounded by 

 irregular wavy lines, due to the truncation of the surrounding 

 tabulae. 



