Mr. R. Etheridge on ChiBtetes tumidus, 195 



so thickened. This is probably the fossil figured by Ure in 

 his 'History of Rutherglen and E, Kilbride'*, and described 

 by Fleming as Gellepora TJrii^. If this is so, Ure was the first 

 to figure Chcetetes tumidus j and it, like many of his figures, 

 is very faithfully drawn. 



When decorticated the tube-walls of C. tumidus are con- 

 siderably reduced in thickness, when compared with the 

 thickened external surfaces. 



Fig. 2 represents a vertical microscopic section of a portion 

 of a branch, where in the central portion, as has been pointed 

 out by M'Coy J, the tubes are vertical and abruptly diverge 

 to the surface, where they open at right angles. The internal 

 wall of each is circular, the external hexagonal or polygonal, 

 becoming thinner towards the imaginary axis of the coral. 

 The vertical portion of the tubes in a transverse section 

 presents the appearance of an axis of cellular tissue (fig. 3). 



Both M'Coy and Edwards and Haime indicate the existence 

 of tabulae. The former says, " diaphragms about the diameter 

 of the tubes apart "§ ; the latter do not mention these structures, 

 but they distinctly figure them ||. On the other hand^ Prof. 

 De Koninek, in his description of MonticuUpora tumida^ states 

 that although he had examined numerous Irish and Belgian 

 specimens, yet he had failed to discover any trace of tabulse 

 {planchers). In fig. 3, which is a ti-ansverse section of fig. 2, 

 the tabulae may be distinctly seen as delicate lines in that por- 

 tion of the tubes at right angles to the general axis, at which 

 point the walls in some specimens appear to be more or less 

 constricted. 



EXPLANATION OF PLATE XI. figs. 1-3. 



Fig. 1. Portion of Chcetetes tumidm, Phil., somewhat enlarged. 



Fig. 2. Vertical section of portion of another specimen, showing the 



central vertical and lateral horizontal portions of the tubes. 

 Fig. 3. Transverse section of the same, showing the tabulae passing across 

 the horizontal portion of the tubes, and also the central vertical 

 tubes. Figs. 2 & 3 are considerably enlarged. 

 [I have to thank my friend Mr. II. M. Skae for the very careful 

 dravsdngs accompanying these notes.] 



* Plate XX. fig. 1. 



t Brit. Animals, 1828, p. 5.33. 



X Brit. Pal. Fo.ss. p. 82. 



§ L. c. p. 83. 



Il Monog. Brit. Foss. Corals, pi. xlv. fig. 3 if. 



