670 
Proceedings of Royal Society of Edinburgh. [sess. 
§ 2. Elliptici. 
Outline roundly or elongately elliptical. 
(a) Elongately elliptical. 
L. ellipticus. Grev., Trans. Micr. Soc. Lond ., 1865, p. 99, 
pi. viii. fig. 6. — Major axis ’0775 to *105 mm., from 2 to 2f times 
minor, the extremities of the major axis acute. Surface but 
slightly convex. Markings delicate ; areolae 2 to 3^ in ‘01 mm.; the 
band adjacent to the border narrow indistinct, with the subradial 
lines 4 to 4J in -01 mm. 
Habitat.- — Cambridge deposit, Barbados (Johnson !) ; “ Barbados ” 
(Greville ! Johnson !). 
(p) Roundly elliptical. 
L. oblongus , Grun. Cleve and Moller, Diat., No. 276. — Major 
axis *04 to "05 mm., about twice the minor ; the extremities obtuse. 
Surface slightly convex. Markings delicate; areolae 4 in '01 mm.; 
subequal or slightly smaller adjacent to the border, without order. 
Border narrow, sharply defined. 
Habitat. — California (Cleve and Moller !). 
L. ovalis. Grev., Trans. Micr. Soc. Lond., 1865, p. 5, pi. i. figs. 
15, 16. — Major axis *04 to '06 mm., from 1-f- to 1^ times minor. 
Surface markedly convex. Markings prominent; the areolae towards 
the centre sometimes imperfect; the band adjacent to the border 
irregular, narrow ; apiculi irregular, inserted at the angles of the 
areolae. 
Greville represents the girdle as a narrow hyaline band extending 
for a short distance beyond the convex portion of the valve. 
Habitat. — Cambridge deposit, Barbados (Johnson !) ; Oamaru 
deposit (Grove !). 
L. marginatus. Grove MS. — Major axis *0475 mm., about 
1J times minor; extremities obtuse. Surface slightly convex. 
Markings robust, areolate ; the areolae irregular and unequal, 2 to 3 in 
'01 mm., largest at the centre bearing a few faint rounded granules ; 
marginal band distinct, its outer edge crenate. Border narrow, 
hyaline. — (PI. III. fig. 13.) 
Habitat. — Oamaru deposit (Grove !). 
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