Vol. 68.] sTJCCESsiOiSr in the north-west of ei^gland. 



565 



The corallum is traversed by a system of large perforations or 

 tubes, arranged on a definite plan. This is found in all well-pre- 

 served specimens, though it is liable to slight variation in detail. 



Eound the base of the wall of each calyx runs a polygonal or 

 roughly circular perforation or ring-canal, which follows the contour 

 of the wall ; this lies just inside the angle formed by the junction of 

 the wall with the floor of the calyx, and slightly below the level 

 of the floor. Thus the base of each wall is traversed by two such 

 tubes bordering the margins of two contiguous corallites (fig. 4^ 

 below). Prom these ring-canals branches are given off", which open 

 by pores into the floor of the calices near the base of the walls 

 (fig. 5). Other branches are given off in the opposite direction 

 from the ring-canals and traverse the wall horizontally, connecting 

 the ring-canals of two adjacent corallites (fig. 6). Other pores 

 are also occasionally seen, opening higher up on the walls of the 

 calices; these are, however, more irregular in their distribution. 



Figs. 4-6. — Vaunhania cleistop oroides, gen. et sp. nov, 



5 [Natural size.] 



6 [Natural size.] 



The pores opening round the basal margin of the calices are fairly 

 numerous, and are placed close together, the distance between 

 them being generally not much greater than the diameter of the 

 pores themselves (fig. 5). 



In microscopic sections the walls and floors of the corallites 

 exhibit a finely- crystalline fibrous structure, similar to that which 

 characterizes many recent corals. The long axes of the fibres are 

 arranged perpendicularly to the walls and floors of the calice.^ 

 (fig. 4, above). There is no trace of the trabecular structure figured 

 by Nicholson in his descriptions of Cleistopora and Palceacis, while 

 tabulae are entirely wanting. This compact fibrous coenenohyma i& 

 perforated by the tubes described above ; and, in the neighbourhood 

 of the tubes, the fibres are arranged in a radial manner perpen- 



