Dr. J. W. Gregory — Egyptian Corals. 245 



arrangement is seldom seen. There are usually three primary 

 septa on one side and four or five on the other ; the septa are rarely 

 bilaterally symmetrical, and the arrangement is heptameral or 

 octaraeral, rather than hexameral. Primary septa highly exsert. 

 Columella, massive, flat-topped. 



Dimensions. 



Horizontal laminae ... ... ... ... 5 in 12 mm. 



Average diameter of cor allite ... ... ... 6-5 mm. 



Average distance of calicinal centres ... ... 11mm. 



Distribution. — Middle Miocene — Helvetian : Egypt, east side of 

 Wadi Jiaffra, north-east of Cai-avanserai No. 8, on road from Cairo to 

 Suez ; Coll. Geol. Surv. Egypt, No. 644. 



Description of Figures. — PI. VIII, Fig. 4a, part of upper surface 

 of a corallum, nat. size ; Fig. 4c, side view of the same specimen, 

 showing lamellar growth, nat. size ; Fig. 46, one corallite, X 2 diam. 



Affinities. — In Duncan's diagnosis of Stylophora he states that 

 "the calices are rather deep," as is the case in the type species, 

 S. digitata (Pall.), and the characteristic forms of the genus. The 

 two corallites of S. similis (May.-Eym.) figured as PI. VIII, Fig. 6, 

 are typical forms of the Eocene group of Stylophora, which agree 

 closely with the recent species. Another series of species is, however, 

 included in the genus which have larger corallites and raised, exsert 

 septa. S. asymmetrica is the extreme form of this group, and I felt 

 at first that it ought to be placed in a new genus. But the essential 

 characters are those of the true Stylophora ; the difference is due to 

 the much greater size of the corallites, and to the fact that the calioe 

 appears superficial, as it is usually raised on the exsert septa. But 

 the calice is really deep, as it occupies a depression surrounded by 

 the raised septa ; and in some corallites the septa end below the 

 surface of the corallum. 



The nearest ally of this species is probably S. macrotheca, Ach.,^ 

 in which, however, the corallites are much smaller, the distance 

 between the calicinal centres being only from 2-5 to 3 mm., so 

 that they are about a quarter of the size of those of S. asymmetrica. 



Another coral which presents some striking resemblances is 

 S. suhreticulata, Eeuss,^ a well-known Helvetian species from the 

 Oberer Tegel of Grand. The Egyptian coral differs, however, by 

 the greater size of the corallites, by the greater prominence of the 

 secondary septa, and by the asymmetry of the septa. The costa3 

 occur, moreover, as raised lines, whereas in S. suhreticulata the 

 exotheca is ornamented by radial series of coarse granules. 



From the typical Oligocene set of species, e.g., S. distans (Leym.),* 



1 A. d'AcMardi, "Cor. Eoc. Fruili," pt. iii : Atti See. tosc. Sci. nat., vol.. i 

 (1875), p. 178, pi. xiv, fig. 2. 



- A. E. von Reuss, " Foss. Kor. oster.-uug. Mioc." : Denk. Akad. "Wiss. "VTien, 

 vol. xxxi (1871), p. 250, pi. v, fig. 10 ; pi. vii, fig. 1 ; pi. xiii, fig. 5. The secondary 

 septa are shown only in pi. vii, fig. lb. 



^ A. Leymerie, "Mem. Terr, a Nummul. Corbieres " : Mem. Soc. geol. France, 

 ser. 2, vol. i (1844), p. 358, pi. xiii, fig. 6. Also Von Reuss, " Pal. Stud. alt. Tert. 

 Alpen" : Denk. Akad. Wiss. Wien, vol. xxviii (1868), p. 24, pi. ix, fig. 2. 



