20 Transactions of the Society. 



forms confusedly intermingled (pi. II., figs. 3, 7). The rays of the 

 former are from 0*14 to 0*22 mm. in length, and about 0-03 mm. 

 in thickness. The exterior surface of the dermal layer appears to 

 be composed of very delicate linear spicules, regularly arranged ; 

 in one instance they are disposed concentrically round a small 

 pore-like aperture (pi. II., fig. 10). 



Distribution. — P. globularis is by far the most numerous species 

 of the genus ; out of a total of 2902 specimens from the English 

 Chalk which I have examined, 2357, or slightly over 81 p.c, 

 belong to it. Its earliest appearance is at the base of the Middle or 

 Turonian Chalk in the zone of Rliynclionclla Cuvieri at Dover and 

 the South Devon coast. It is distributed generally in all the 

 higher zones of the Chalk, and becomes more numerous and larger 

 in size till reaching its maximum in the zones of Micraster cor- 

 anguinum and Marsupitcs. The loaf- and cushion-shaped forms 

 occur chiefly in the Marsiqritcs zone at Margate and the Thanet 

 coast, and in the Bel. mueronata zone at Ballard Cliff and Studland 

 Bay, on the Dorset coast. It is common in the Chalk of Flam- 

 borough Head and Sewerby, on the Yorkshire coast, where the 

 specimens are small generally. It is also abundant at and near 

 Newhaven and Brighton, and in the Isle of Wight. Inland, it is 

 found plentiful at and near Croydon. Surrey, and sparsely in 

 Hampshire and Wiltshire. 



According to Steinmann, P. globularis is generally present in 

 the Chalk of Middle and Northern Europe. Eeuss and Fritsch 

 record it from the Teplitzer beds (Lower Senonian ?) at Ivutschlin 

 and near Bilin, in Bohemia, and von Hagenow from the island of 

 Biigen. Lately Bavn * has recognised it in the Bryozokalk (Older 

 Danian) of Jutland. 



Porosphccra nuciformis, von Hagenow, sp. (pi. I., figs. 11-18; 



pi. II., fig. 4). 



1822. Zoophyte of a pyriform shape, the nature of which is unknown, Mantell, 



Geology of Sussex, p. 162, pi. xvi., figs. 17, 18. 

 1839. Ceriopora nuciformis, von Hagenow, Neues Jalirb. fur Mia., p. 286, pi. v., 



fig. 9. 

 1872-5. „ „ Geinitz, Palreontographica, vol. xxii., p. 4. 



1879. „ „ Quenstedt, pars. Petrefact. Deutschl., p. 62. 



1900. Porosphasra Woodwardi, Eowe (non Carter), Proc. Geol. Assoc, vol. xvi., 



pt. 6, pp. 304, 344, 361 ; vol. xvii., pt. 1 (1901) pp. 67, 72. 



Sponges free, simple, typically pear-shaped, but occasionally 

 melon- or loaf-shaped, with longitudinal low swellings or ridges, 

 and intermediate shallow grooves which converge to the obtuse 

 pole of the sponge. The number of the ridges variable ; in some 

 specimens they are set closer and more strongly marked than in 



* Kgl. Datiske Vidensk. Selsk. Skrifter, 6 Eakke, xi. 6 (1903) p. 423. 



