12 Transactions of the Society. 



near the opposite side, but without passing through it completely 

 (pi. I., fig. 1). The tubes generally pass straight through the 

 centres of the rounded forms, but they are not definitely oriented 

 in the cushion- or pear-shaped fossils, through which they extend 

 either longitudinally, transversely or obliquely. In the collections 

 examined from the zone of Micr aster cor-tcstudinarmm upwards 

 to the Bel. mucronata zone, out of 1799 specimens of P. globidaris 

 from different localities, there were 321 or about 18 p.c. per- 

 forated ; of this number 147 were completely perforated or natural 

 beads, whilst 174 were partially perforated. In 184 specimens of 

 P. nuciformis from the same beds, there were tubes in 32, or about 

 17 p.c. ; in only 6 instances the tubes extended through ; whilst 

 in 26 they only reached to varying depths in the fossils. 



EXPLANATION OF PLATE I. 



Tlie figures are of natural size except where otherwise indicated. 



Fig. 1. PorospJisera globidaris, Phillips, sp. Large oval specimen, with tubular 

 perforation. Zone of Micraster cor-anguinum ; South Croydon, 

 Surrey. Collection of G. J. Hinde. 



„ 2. Ditto; showing overlapping layers of growth. Zone of Marmpites; Margate, 

 Kent. Collecti >n of Dr. A. W. Eowe, F.G.S. 



„ 3. Ditto ; loaf-shaped. Zone of JJelemnitella mucronata ; Ballard Cliff, Dorset 

 coast. Collection of Dr. Eowe. 



„ 4. Ditto; cushion-shaped specimen. Zone of Bel. mucronata; Ballard Cliff. 

 Collection of Dr. Piowe. 



., 5. Ditto ; of average s ; ze. Zone of Actinocamax quadratus ; Cliff, east of 

 Brighton. Collection of G. J. Iiinde. 



„ (J. Ditto; median section, showing the arrangement of the radial canals. 

 Upper Chalk. Collection of G. J. Hinde. 



,, 7. Ditto ; completely enveloped with a spieular dermal layer. Zoae of B. 

 mucronata ; Ballard Cliff. Collection of Dr. Eowe. 



„ S. Ditto ; partially covered with an uneven dermal layer. Same zone and 

 locality as the preceding. Collection of Dr. Eowe. 



,, !*, 10. Ditto; loaf-shaped specimens, showing faint indications of surface grooves. 

 Zone of Marsupites (Uintacrinui Band) ; Thanet coast. Collection 

 of Dr. Eowe. 



.. 11. Pwosphasra nuciformis, v. Hagenow, sp. Viewed from above, showing the 

 convergence of the grooves at the summit. Zone of Marsupites 

 (Uintacrinus Band); Margate. Collection of Dr. Eowe. 



„ 12. Ditto; side view. Zone of A. quadratus; near Newhaven. Collection of 

 Dr. Eowe. 



„ 13. Ditto; showing closely- arranged grooves. Zone of A. quadratus; Win- 

 chester. Collection of Dr. Kowe. 



„ 14. Ditto; with prominent apex. Zone of A. quadratus ; Sussex coast. Col- 

 lection of Dr. Eowe. 



„ 15. Ditto ; with fragments of the dermal layer. Zone of A. quadratus ; near 

 Newhaven. Collection of Dr. Eowe. 



„ 10, 16a. Ditto ; viewed from above and in profile. Zone of Marsupites (Uinta- 

 crinus Band); Thanet coast, Kent. Collection of Dr. Eowe. 



„ 17. Ditto; viewed from above. Same zone and locality as tho preceding. 

 Collection of Dr. Eowe. 



„ 18. Ditto ; with surface grooves and ridges radiating from several centres. 

 X 2 diam. From same zone as the preceding; Sussex coast. Col- 

 lection of Dr. Eowe. 



