292 



Prof. J. W. Gregory. 



results seem to confirm the old view of the affinity between the Helio- 

 litidse and the Helioporidse, by showing that Polytremacis is truly 

 intermediate between the two families. In that case Polytremacis is of 

 considerable phylogenetic interest as an ancestor of Heliopora. I there- 

 fore venture to submit this paper to the Society which has published 

 the two most important contributions to our knowledge of that im- 

 portant coral. 



2. The Type of Polytremacis. 



Polytremacis was founded by d'Orbigny in 1849, when he gave it the 

 following very inadequate diagnosis [14, p. 11] : — " c'est un Stylophora 

 sans saillies aux calices, ceux-ci simplement creuses. Intervalle d'un 

 tissu poreux, granuleux en dessus. Ensemble amorphe." The only 

 species named is P. bulbosa d'Orb. from the Cenomanian of the lie d'Aix, 

 Charente-Inferieure ; it was defined the following year [15, p. 183] as 

 " espece globuleuse, arrondie a calices assez grands." That species has 

 never been figured, and the type specimen is apparently not available, 

 as Milne Edwards and Haime [5, p. 232] who quoted it, have simply 

 repeated d'Orbigny's statement. P. bulbosa may therefore be dismissed 

 as a nomen nudum, and another type must be found for the genus. This 

 task is easy. D'Orbigny's second reference to Polytremacis was in his 

 * Prodrome de Paleontologie,' where (vol. 2, p. 209) he gives a list of 

 four species. The first of the four is the Heliojpora blainvillei of 

 Michelin [10, p. 27, Plate 7, fig. 6], from the Turonian of Vaucluse. 

 The other three were new species founded by d'Orbigny, apparently 

 on mere varieties of P. blainvillei. The three new species were not 

 figured, and were subsequently accepted by Milne Edwards and 

 Haime on d'Orbigny's authority. There can therefore be no question 

 that of these four species P. blainvillei (Mich.) must be taken as the 

 type of Polytremacis. 



The characters of this species are, however, somewhat doubtful. 

 Michelin's original figure represented a lobed corallum, with one short 

 cylindrical branch ; the calicles are generally crowded and separated 

 by areas about as wide as themselves. The rim of the calicle is notched 

 by a series of sixteen or twenty teeth. 



In 1854 von Keuss [16, p. 136, Plate 24, figs. 4-7] figured a coral 

 from the Turonian of Gosau, and identified it as P. blainvillei. Milne 

 Edwards and Haime [5, p. 232], to whom Michelin's types were easily 

 accessible, accepted the accuracy of the determination, and described 

 von Keuss' figures as " very good." But Lindstrom not only denies 

 the accuracy of the specific identification, but urges that the coral is 

 generically distinct from Polytremacis [9, p. 28]. 



The Polytremacis blainvillei of Michelin diff'ers from that of von 

 Reuss in two respects. The coral thus named by the former author 

 has no lamellar septa, but only a series of " pseudosepta " or septal 



