47 0 Proceedings of Royal Society of Edinburgh. [sess. 
border. Central space and rosette absent. Markings subpearl y, 
robust, pentagonal or hexagonal, each with a faint central dot, 
2J to 3J in ’01 mm., decreasing but little towards the border. 
Border sharply defined, subopaque, broad ; striae evident, 3 \ to 4 
in *01 mm.; a series of closely placed concentric lines sometimes 
visible, the outer edge rugose. Girdle aspect,* with smaller areolae, 
4 to 5 in *01 mm., forming straight or slightly flexuous rows parallel 
to the edge of the girdle; girdle narrow. — Cleve, Bih. k. Sv’Vet.-Ak. 
Handl. Stockh ., 1873, No. 11, p. 4 ; Sch., Atl ., pi. lxii. fig. 8; C. con- 
cavus, Ehrb., pro parte, Abh. Ber. Ak., 1841, p. 412; Mikrog., 
pi. xxi. fig. 4 f (excl. pi. xviii. fig. 38) ; Endidya oceanica , Ehrb., 
Mon. Ber. Ak., 1845, p. 76; Mikrog., pi. xxxv. A, 18, figs. 6, 7 ; 
Balfs in Pritch. Inf., p. 831, pi. v. fig. 70; Moll., Typ. PI. 4, 4, 8, 
Cleve and Moll., Diat., No. 110, 259; Baben., Alg. Europ., No. 
2556 ; H. L. Sm., Diat. Sp. Typ., No. 148 ; Sch., Atl., pi. lxv. 
figs. 10, 12, 13, 15. Coscinodiscus concavus, var. africanus. Kiitz, 
Sp. Alg., p. 125; C. oceanicus , Kiitz., ibid., p. 126; Melosira 
cribrosa , de Breb., W. Sm. in Ann. and Mag. Nat. Hist., 1857, 
p. 11, pi. ii. fig. xv.; Orthosira oceanica, Brightw., Quart. Jour. 
Micr. Sci., 1860, p. 96 ; Endidya minor, Sch., Atl., pi. lxv. figs. 
14, 16; Melosira oceanica, Habirsh, Cat. Diat., ed. 2, § Endidya. 
The specimen named C. concavus by Ehrenberg (Mikrog., pi. 
xviii. fig. 38), from Richmond, approaches the unnamed organism 
figured by Gregory from the Glenshira Sand (Trans. Micr. Soc. Lond., 
1857, p. 85, pi. i. fig. 52), but is distinct from the present species. 
C. concavus, var., Sch. (Atl:, pi. lix. fig. 16) is C. antiguus, Grun. 
W. Smith followed de Brebisson’s determination of Melosira cribrosa 
provisionally, separating it from Coscinodiscus only because he 
believed that the frustules might occur concatenated. C. concavus, 
var. africanus, from Oran, was first differentiated by Ehrenberg 
as C. concavus africce (Mon. Ber. Ak., 1844, p. 79), with 3J to 4 
markings in '01 mm., but this is inadequate on which to establish 
a variety. Cork specimens, authenticated by Grunow as Endidya 
minor (Sch., Atl., supra), agree with Gregory’s C. concavus. 
Specimens sometimes named Endidya oceanica differ from C. con- 
cavus only in showing the markings somewhat more irregular. 
* This applies to specimens hitherto named Endidya. 
+ Specimen not typical. 
