THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. V. 



No. VIII.— AUGUST, 1898. 



OE,ia-IJ^.A.X. J^S-TIGLES. 



I. — MiLLESTROMA, A CrETACEOUS MiLLEPOROID CoRAL FROM EgYPT. 



By J. W. Gregory, D.Sc, F.G.S., of the British Museum (Natural History). 

 (PLATE XIII.) 



THE wide geographical distribution of the MilleporidEe is 

 a clearer proof of the geological antiquity of the group than 

 any evidence yielded by pala3ontology. For Millepora has no 

 known Mesozoic or certain Lower Cainozoio representative, and 

 is thus separated by a great gap from the Palsezoic Hydrocorallinse, 

 whence it is probably descended. But the Stromatoporoids dis- 

 appear at the end of the Palgeozoic, and I am not aware that any 

 coral has been described, which helps to connect that group and 

 the Cainozoic Milleporids. 



The question is complicated by the difficulty of distinguishing 

 between the skeletons of those Bryozoa, Hydrozoa, and Anthozoa 

 which consist of masses of parallel tubes. ^ In each of these groups 

 there are genera in which the skeletal structures consist of bundles 

 of long, narrow, cylindrical or prismatic tubes, which are of two 

 sizes, and are divided into chambers by fiat platforms or tabulge. 

 The problem how to determine to which group a particular fossil 

 with these characters may belong has not yet been solved. This 

 is not surprising since the same doubt also occurs respecting 

 some living species. Thus, according to most authors, Heteropora 

 pelliculata, Waters, is a Bryozoan ; but according to WentzeP it 

 is a Favositid. In regard, to the recent forms, even if we have 

 no knowledge of the soft parts, we can get some light from the 

 histological structure of the skeleton. But this clue is lost ia 

 the case of most of the fossils; for as a rule the calcareous skeleton is 

 perforated by numerous pores and canals, so that it is open to attack 

 by solvents ; hence the hard tissues have genei-ally been dissolved 

 and redeposited in a crystalline form. During this process the 



^ The difficulty presented bv these multitubular fossils I have previously stated 

 in the " Catalogue of the Jurassic Bryozoa" (Brit. Mus., 1896), pp. 3-6. 



^ J. Wentzel, " Zur Kenutniss der Zoantharia Tabulata " : Denk. Akad. "Wiss. 

 Wien, vol. Ixii (1895), p. 496. The species is referred to as S. Neozelanica. 



DECADE IV. VOL. Y. ^NO. Till. 22 



