674 
Proceedings of Royal Society of Edinburgh. [sess. 
the interval minutely punctate ; at subregular intervals narrow 
hyaline straight lines at right angles to the edges of the valve. 
The fasciculi are hounded by two adjacent radial rows, some- 
what more conspicuous than the intervening rows. In one of the 
valves in Greville’s collection it is possible to trace downwards 
from the central space a cylindrical siliceous tube which is of 
sufficient length to have passed to a plane corresponding in position 
to the edges of the valve. 
Habitat. — Cambridge deposit, Barbados (Greville ! Johnson !); 
“Barbados” (Greville ! Johnson !). 
P. spiniferus, sp. n. : — Circular. Diam. *0875 mm. Surface 
dome-shaped. Central space circular, ’0075 mm. broad. Markings 
areolate, subequal, 7 in *01 mm.; rows radial, straight; fasciculi 
evident; bounded by two rows of more prominent submuriform 
areoke; spines robust, conical, about *03 mm. long, interfasciculate, 
forming a circlet at about” J of distance between central space and 
edge of valve. Girdle cylindrical, *0375 mm. broad; a narrow 
hyaline band at each extremity ; the clear substraight lines at right 
angles to its edges distinct. — (PI. III. fig. 19.) 
Habitat. — Cambridge deposit, Barbados (Johnson !). 
P. oblongus. Grev., Trans. Micr. Soc. Lond ., 1863, p. 63, 
pi. iv. fig. 5. — Subacufcely elliptical. Major axis -05 mm. long, 
about times minor. Surface sloping gradually downwards from 
edge of central space. Central space roundly elliptical, with major 
axis corresponding in direction to minor axis of valve. Markings 
angular, decreasing regularly and somewhat rapidly from central 
space to border; around the central space 4J-, at border 10, in 
•01 mm. ; rows radial, substraight. Border narrow, hyaline. — 
P. ovalis, Grev., ibid. ; Explan. pi. iv. fig. 5 ; Craspedodiscus 
oblongus , Grun.; Sch., Atl., pi. lxvi. figs. 7-9. 
This species approaches in appearance Coscinodiscus oblongus , 
Grev. {Trans. Micr. Soc. Lond., 1866, p. 4, pi. i. figs. 9, 10). 
Habitat. — Barbados deposit (Johnson!). 
P. Stolterfothii. Cstr., Diat. Ghall. Exped ., 1886, p. 139, 
pi. xii. fig. 8. — Bhombic, with angles obtuse. Major axis ’077 mm. 
long, about l/^- times minor. Surface slightly convex towards 
