4 Transactions of the Society. 



whilst the allied conical, hemispherical, and depressed forms are 

 definitely assigned to 0. concava, Lamk. sp. 



F. A. Roemer, in 'Die Spongitarien des Norddeutsehen Kreide- 

 gebirges' (Palceontographica, vol. xiii. (1864) p. 56), placed Tragos 

 globularis, Iieuss ( = P. globularis, Phill.), as a synonym of Achilleum 

 globosum, v. Hag. 



In the ' Seeschwiimme des mittleren und oberen Quaders ' 

 {Palmontographica, vol. xxii. (1872-5) p. 4), H. B. Geinitz pointed 

 out that the resemblance in outer form between Ccriopora nuci- 

 formis, v. Hag. (= P. nuciformis) and Achilleum globosum ( = Plin- 

 thosella squamosa, v. Zitt.) is so close that they may readily be 

 mistaken for each other. Geinitz placed this latter sponge with 

 the Lithistidce, where it rightly belongs. 



H. J. Carter, in the Ann. and Mag. Nat. Hist., s. 4, vol. xix. 

 (1877) p. 64, and s. 5, vol. i. (1878) p. 298, described under the 

 names, first of (?) Bradya tergestina, and afterwards of Millepora 

 Woodwardi, a new species of Porosphcera, characterised by branched 

 canals which radiate from points on the surface. It is regarded 

 as a Hydrozobn with a structure similar to that of Parkcria. The 

 forms occur in the Grey Chalk near Dover, and the types are now 

 in the British Museum (Natural History), South Kensington. 



In his memoir ' Ueber fossile Hydrozoen aus der Familie der 

 Coryniden' (Palceontographica, vol. xxv. (1878) p. 120, pi. xiii., 

 figs. 8-12), Dr. G. Steinmann referred Millepora globularis to a 

 distinct genus, Porosphaira, belonging to the Hydrocorallina?. The 

 skeleton is stated to consist of anastomosing calcareous fibres, like 

 those of Parkcria, and their microstructure is distinctly radiate. 

 The author recognises the close resemblance in outer form of 

 Porospltcera to Sponges, but stated that the definite connected cal- 

 careous skeleton is quite unknown in existing sponges, though it 

 occurs in numerous fossils. The various forms of Porosphcera, 

 including P. Woodwardi, Carter, are regarded as belonging to a 

 single species, P. globularis, Phillips. 



In the Elcmcntc der Palceontoloejic (1888) p. 77, fig. 73, by the 

 same author and Dr. Doderlein, Porosphcera is retained in the 

 same systematic position. The Gastroporen are stated to be 

 radial and numerous, in other respects like Millepora. 



Dr. F. A. Quenstedt, in the Petrcfaktenkunde Dcutsch lands, 

 vol. vi. (1879) p. 262 ; Atlas, pi. 153, figs. 1-12, referred a series 

 of the usual forms of P. globidaris to Ccriopora nuciformis, v. Hag., 

 and considers them as Bryozoa. Quenstedt farther mentioned that 

 amongst a suite of specimens sent to him direct by v. Hagenow 

 as examples of his Achilleum globosum, some were genuine forms 

 of Ceriojyora nuciformis, whilst others were definite sponges. 



In the Handhuch der Palceontologie, vol. i. (1879) p. 288, 

 Prof. v. Zittel accepted Steinmann's determination of Porosphcera, 

 and placed the genus in the family Milleporida^ ; in the same 



