444 DE. G. J. HINDE ON NEW EOSSIL8 [Aug. 1 896,. 



Dr. Kunth ! next undertook a description of the genus, but he 

 professedly based his observations on Ptychocliartocyathus laxus? 

 Ludwig, a coral which he considered to be congeneric with Palo?,acis - r 

 the form that he describes and figures, however, is by no means 

 similar to that placed under this name by Ludwig, but appears rather 

 to belong to Hydnopora (?) cyclostoma, Phillips, 3 first described by 

 Phillips from the Carboniferous Limestone of Yorkshire. 



Prof, de Koninck 4 followed nearly in the same path as Kunth r 

 by accepting Hydnopora (?) cyclostoma, Phill., as a genuine Palceacis, 

 and then relying on its characters for the definition of the genus. 

 Prof. Perd. Ecemer, 3 on the other hand, maintained that H. (?) cy- 

 clostoma was not congeneric with Palceacis, mainly on the ground- 

 that it was an attached and not a free form, but subsequently 6 he 

 retained it in the genus, though still regarding it as probably 

 distinct. 



In 1878 Messrs. Etheridge and Nicholson 7 published an excel- 

 M lent paper, ' On the Genus Palceacis and the Species occurring in. 

 British Carboniferous Rocks,' in which, for the first time, reference 

 is made to the microscopic structure of the various forms. These 

 authors, however, agreed with De Koninck that H. (?) cyclostoma,. 

 Phill., really belonged to the genus, and as a consequence the 

 characters of this particular form, which is very fully described 

 and illustrated, largely enter into their definition of the genus. 

 They reach no final decision as to the systematic position of Palceacis r 

 though they consider it more closely allied to sponges than to corals. 

 Since then, however, Prof. Nicholson 8 has fully acknowledged that 

 Palceacis is a perforate coral, but it should be remembered that 

 this conclusion refers rather to Hydnopora (?) cyclostoma, Phill.,. 

 than to the type-species of the genus. 



In order to determine the question as to the rightful characters 

 of Palceacis and whether Hydnopora (?) cyclostoma, Phill., can pro- 

 perly be incorporated in this genus, it will be necessary to consider 

 separately the main features of P. cuneiformis, M.-Edw., the un- 

 doubted type of the genus, and of H. (?) cyclostoma, Phill., and 

 then compare them together. 



Taking first P. cuneiformis, a difficulty is experienced at the 

 outset owing to the rarity of examples of this species and their 

 unfavourable condition of preservation. I have had mainly to 

 rely upon a few specimens, obtained from the same beds at Spergen 

 Hill as those that yielded the type-forms, with which they correspond 

 very closely. They are, however, siliceous and replaced in part by 

 beekite, so that their microscopic characters are obscured. The 



1 Zeitschr. deutsch. geol. Gesellsch. vol. xxi. (1869) p. 183. 



2 Palseontographica, vol. xiv. (1866) pp. 189, 231, pi. xlvii. fig. 14, pi. lxix- 

 fig. 2a. 



3 ' Geol. Yorkshire,' vol. ii. (1836) p. 202, pi. ii. figs. 9 & 10. 



4 'Nouv. Kechercb.es Anim. foss. Terr. Carb. Belgique,.' 1812, pt. L 

 pp. 154-161. 



3 ' Lethsea Palaeozoica,' Atlas, 1876, pi. xxxix. Explanation. 



6 Ibid. Text, 1880, p. 515. 



7 Ann. & Mag. Nat. Hist. ser. 5, vol. i. (1878) pp. 206-227, pi. xii, 

 * ' Man. of Palaeontology,' 3rd ed. vol. i. p. 310. 



