PROF. T. M. DENCAN ON A NEW GENUS OF JIA DREPOR ARIA. 31 



collection of the Geological Society. There is, however, a much 

 weathered specimen of Septastrcea Forbesi, Ed. & ~H..,=*GI>/phastrcea 

 Forbesi, with the name of Dr. Koch upon the tablet as that of the 

 collector. The specimen is a very instructive one, and it shows how 

 weathering may destroy all those structures which characterize a 

 species. There is only one calice in the rather large colony which 

 indicates that there was once a small columella, and the intercalicular 

 groove is almost destroyed in every part of the coral. The edges of 

 the neighbouring corallites are often sharp from removal of the inside 

 of the calices. The study of this specimen proves how thoroughly 

 palaeontologists may be deceived by describing indifferent specimens. 



EXPLANATION OF PLATE III. 



Fig. 1. The colony of Glyphastrza. Forbesi, in outline ; nat. size. 



2. Part of the fractured stem, magnified, a, corallite undergoing fissi- 

 parity ; of, a part dividing from a\ b, corallite undergoing fission ; 

 c, corallite with a confused septal arrangement; d, a bud with six 

 primaries, a secondary septum, and a columella; e, corallite showing 

 a columella ; /, corallite commencing fission (compare the part 

 nearest the axis of the stem with a', in which the process has been 

 completed). 



3. Three weathered corallites, magnified, taken close below the position 

 of the c dices ; fission in progress in two, and the columella visible 

 in the third. 



4. Sections of corallites, one undergoing fission, magnified. Specimen in 

 the British Museum. 



4'. Two calices corresponding to the fissiparous corallite of fig. 4, magnified. 



5. Some calices, magnified. 



6. Section of a corallite showing 'complete endotheea and a ring-shaped 

 columella, magnified. Specimen in the British Museum. 



7. Longitudinal section of a corallite showing close successive endothecal 

 dissepiments below that which closes the calice inferiorly, magnified. 

 British Museum specimen. 



8. A similar section showing successive layers of endotheea in relation to a 

 columella, magnified. British Museum specimen. 



9. Part of a longitudinal section of a corallite showing a discontinuous 

 — columella, magnified. British Museum. 



10. The central superficial nodule of a columella, magnified. British 

 Museum. 



11. The position of the ribbon-shaped part of the columella, placed between 



the inner ends of two opposite primary septa, magnified ; more or 

 less diagrammatic. 

 I.X2 - Primary septa joining at their inner ends, magnified ; diagram. 

 13, 14. Junction of septa accompanied by more or less columellar struc- 

 ^ ture in 14; a section magnified. Specimen in British Museum. 



15. View of septa and columella from above, magnified. British Museum. 



16. Twisted septal ends forming a false columella, magnified. 



Discussion. 



Dr. Hinde remarked on the interest attaching to the specimens. 

 He inquired if one of the specimens on the table belonging to the 

 Society was .not the type of M. -Edwards and Haime. He thought 

 the prolongation of the septa across the calice indicated merely 

 a tendency to lissiparity, and was not a generic character. He was 

 not sure if there was a columella distinct from this prolongation, 



