).54 MADREPORARIA. 



are hardly distinguishable ; thick near the walls, but verj' thin near the columellar tangle ; 

 drawn straight and separate in the figure, but described as slightly wavy and with the 

 tertiaries fusing with the secondaries ; perforate through their whole length, denticulate or 

 granulate along theu' upper edges, and laterally echinulate. The columellar tangle is 

 conspicuously reticular and hardly raised. Between it and the septa rudimentary pali 

 sometimes occur. 



Only one specimen, about 4 inches square and 1 inch thick, is known. The figures 

 are not quite in harmony with the text. A wall reticulum consisting of a single row of long 

 rectangular meshes, with no trace of median thread, is enough to suggest caution. The 

 description of the rudimentary pali is not clear, while the figure gives no help. 



Eichwald compared the coral with the Middle Eocene Goniopora Sussex 1 (" Litharcea 

 Wehsteri "), but says it was explanate and not spherical, a difference depending solely upon 

 accidental conditions. G. Sussex 1 was spherical or thick encrusting, according as the pebble 

 on which it grew was small or large. The thicker wall and echinulate septa of the Crimean 

 form were also supposed to differentiate it from G. Sussex 1. None of the Sussex forms show 

 a wall reticulum like that figured for the Crimean specimen. 



The most interesting point about this coral is that it is the very earliest known 

 representative of the genus Goniopora. It is important to note that it is not very far 

 removed from the ideal primitive Goniopore sketched in the Introduction. It differs, however, 

 in a few points. The wall should have been a simpler reticulum, probably with a median 

 thread, and the fusion of tlie septa should have been more pronounced. 



The great gap between this solitary coral from the lower Cretaceous beds, and the supposed 

 period of the greatest development of the genus in the early tertiaries, is by no means filled up 

 by the three forms from the later Cretaceous beds of Austria-Hungary. Indeed until the gaps 

 shown on the Geological Table, p. 168, are filled up, our knowledge of the genus must be 

 regarded as very rudimentary. 



GROUP XII.— SOMALILAND. 

 144. Goniopora Somaliland (i)l. 



[Somali Plateau, in the Cherty Limestones, overlying the Xerinjea Limestones, above Miriya 

 Pass, and around God-la- Yareh, south of Bur-dab (8" 30' N ; 46° 30' E.) (Eocene) ; Coll. 

 F. B. Parkinson ; British Museum.] 



Litharcea parkinsoni, Gregory, Quart. Journ. Geo. Soc. LVI. (1900), p. 37, pi. ii. figs. 13 and 14. 



Description. — The corallum formed what appear to have been parts of short, somewhat 

 flattened and rather angular stems, up to 25 mm. in breadth and 18 mm. thick ; with smaller 

 pieces of the same character, about 10 mm. thick. 



Calicles 3-4 mm. in diameter, very shallow, not very sharply polygonal. Walls slightly 

 but irregularly raised, here and there as a sudden ridge, occasionally with a median very zig- 

 zag thread, but more often appearing as a pronounced, not very thick, reticulum. The 24 septa 

 show traces of the typical fusions ; they are rather long, wavy, sometimes appearing to run 

 over the wall. The columellar tangle was not large, but appears to have been fairly clearly 



