Polytremacis and ihe Ancestry of ITelioporidce. 



299 



Distribution. — Turonian, Uradu limestone. Uradu near the Rugga 

 Pass, Somaliland. (The Eugga Pass is in 45° 22' E. and 10° N.) Col- 

 lected by Mrs. E. Lort Phillips. Type in British Museum, E4150. 



Affinities. — The nearest ally of this species is H. edwardsi Stol., from 

 which it differs by having smaller and less distant calicles, and some 

 areas of angular pseudocaeca. 



Species 2.— Heliopora edwardsi Stoliczka, 1873. ' Pal. Ind., Cret. 

 Fauna, S. India,' vol. 4, Part IV, p. 53, Plate 11, fig. 11. 



Characters. — Corallum incrusting ; calicles 1 mm. in diameter, and 

 from 4 to 5 mm. distant. Coenenchymal caeca numerous and minute. 

 Septal ridges 18 in number. 



Stoliczka describes this species as almost identical with Heliopoin 

 ccerulea. 



Distribution. — Cenomanian. Utatur Group. E. of Kauray, S. India. 



Species 3.— Heliopora boettgeri. Fritsch, 1878. " Kor. Nummuli- 

 tensch. Borneo," ' Palseontogr.,' Suppl. Ill, Lief. 1, Part III, p. 103, Plate 

 17, fig. 4. ■ 



Characters. — Corallum a thin incrustation, 1 to 4 mm. thick. Calicles 

 1 mm. in diameter. Septal ridges, ,16-24. Calicles widely spaced, 

 with small, round caeca. 



Distribution. — Eocene. Borneo. 



Genus 2. — Polytremacis, d'Orbigny, 1849. 

 Synonyms — 



Heliopora, pars, Michelin, Edwards and Haime, et alii. 

 Dactylacis, d'Orbigny. 



Definition. — Helioporidse with thick-walled calicles. 



Type Species. — Heliopora blainvillei, Michelin, 1841. 'Icon. Zooph., 

 p. 27, Plate 7, fig. 6. 



Affinities. — This genus is accepted by Milne Edwards and Haime, 

 von Reuss, and Stoliczka for the Helioporids with long septa, which 

 almost meet in the middle of the calicles. But von Eeuss has 

 remarked on the difficulty in using this uncertain character, and con- 

 cludes that the separation of the genera is not based on any very firm 

 ground. 



The character of the calicular walls appears more reliable, especially 

 as it appears to be geographically distinctive, Heliopora being limited 

 to the Indian Ocean and Pacific, while Polytremacis occurs in the Upper 

 Cretaceous and Lower Cainizoic of central Europe and France. The 

 two genera seem very closely allied, and I should not be surprised if 

 they are ultimately united. 



vol. lxvi. 



