'AS2 



Dr. J. E. Diierdon on the nehi(ionsJiij)s 



been made to bring the Rugosa eitlier into line with modern- 

 hexamerous corals, or to associate them with otiier groups ; 

 in the sug^^estions uf Quelch (1886) and Ogilvie (1893), 

 iiowover, minor considerations of structure have prevailed. 

 G. von Koch (1896), with his mature experience of coral 

 morphology, lias tried to show how from the six pairs of 

 ])rimary njesenteries, arranged as in recent corals, a primitive 



Tr lusverse section through tlie tip of a corallum. The dark median lines 

 of only six primary septa are present, but the outlines of the septa as 

 a whole are not clearly determinable, their surfaces beinjj: fused 

 throughout. The two median septa are represented by a continuous 

 line, while the other four septa are arranged as an upper bilateral 

 pair and a lower bilateral pair. Of the six primary iuterseptal spaces, 

 the two upper are slightly smaller than the others. By iuterseptal 

 spaces may be here understood the interval between the dark lines 

 of two contiguous septa ; the septa are so broad as to occupy the 

 ■whole of the calicinal cavity, leaving no interseptal loculi. The 

 descriptive terms upper and lower are used merely to indicate the 



{)osition of the parts in relation to the section as a whole, and can 

 lave no morphological significance until the relationship of tlie 

 ditTerent aspects of the coral with modern forms is established. In 

 all the figures the upper border corresponds with the convex side of 

 the coral and the lower with the concave border ; the primary septa 

 are indicated by the Roman numeral I. and the later septa by the 

 letters A-I), according to their order of appearance within the four 

 primary interspaces. 



septal tetramerism might be obtained ; while the distinguished 

 Ijelgian naturalist E. van Beneden (1897), assuming a 

 primary four-rayed condition, places the group near the tetra- 

 meral Scyphomedusa, far removed from the hexamerous 

 Madreporaria and Actiniaria. 



