Vol. 52.] FROM THE CARBONIFEROUS LIMESTONE. 443 



Quarry and at Hannaford Quarry, near Barnstaple, North Devon. 

 Only casts are here found ; they are associated with casts of radio- 

 laria, trilobites, etc. 



Remarks on the Genus Paheacis (Haime), Milne-Edwards. 



Various and conflicting opinions have been advanced as to the 

 -characters and systematic position of this genus. It has been 

 placed alternately with corals and sponges, and, though latterly it 

 has been generally regarded as a perforate coral, its real characters 

 have not yet been definitely settled. This uncertainty appears to 

 me to be in part due to the fact that some authors have placed in 

 r the genus certain forms which widely differ from the typical species, 

 and have then defined its characters more from these foreign forms 

 than from the original types. 



As is well known, Milne-Edwards l founded the genus on some 

 ■small wedge-shaped specimens from the Subcarboniferous Limestone 

 of Spergen Hill, Indiana, which are described as having the polypary 

 free, with a finely vermiculate ccenenchyma. The calices were stated 

 to be divided by two large septa, and also furnished with thirty to 

 forty fine striae, supposed to represent septa which had been de- 

 stroyed. The author was not positive as to the coral-nature of 

 these bodies, but he provisionally placed the genus with the Madre- 

 poridse and named the type-species Palceacis cuneiformis. It may 

 here be remarked that later observations have shown that the author 

 was mistaken, both with respect to the vermicular ccenenchyma 

 and the two large septa in this species ; but, as he gave fairly good 

 figures of the forms described, no doubt has remained as to their 

 identity. 



The same species, with others allied to it, were independently 

 described nearly at the same time by Meek and Worthen 2 under the 

 generic term Sphenopoterium. They were considered to be corals 

 -allied to Cyathoseris, M.-E. & H. ; but a few years afterwards these 

 same authors, 3 relying on the authority of Prof. Verrill, removed 

 the genus from corals and placed it with sponges. It is now 

 acknowledged that Sphenopoterium is a synonym of Palceacis, and 

 priority has been generally conceded to this latter. 



In 1866 K. von Seebach 4 referred the genus to perforate corals 

 #,nd proposed two new species, which have since been regarded as 

 synonyms of Palceacis obtusa, Meek & Worthen, sp. This author 

 does not appear to have examined any examples of the type-species 

 or microscopic sections of the forms described, but states that there 

 was a vermiculate perforate ccenenchyma, in which the individual 

 calices were enclosed, and he agrees with Milne-Edwards in assigning 

 the genus to the Madreporidae. 



1 Hist. Nat. CoralL vol. iii. (1860) p. 171, Atlas, pi. b 1. fig. 3. 



2 Proc. Acad. Nat. Sci. Philad. I860, p. 447. 



3 Geol. Surv. Illinois, vol. ii. (1866) p. 145. 



4 Nachr. k. Gesellsch.Wiss. zu Gottingen, 1866, p. 241 ; also Zeitschr. deutscb. 

 :geol. Gesellsch. vol. xviii. (1866) p. 304. 



