1888 - 89 .] Mr John Rattray on the Genus Coscinodiscus. 523 
about twice its greatest breadth, its outer edge more distinct, 
convex towards the border, its inner less curved, the extremities 
obtuse ; the slope to the border gentle. Markings areolate, sub- 
equal, 3 to 3| in *01 mm. on the depression round, granular ; with 
hyaline interspaces, the central papillae prominent; rows radial, 
straight; secondary oblique decussating rows uniformly curved, 
manifest. Border relatively narrow, with coarse evident, subradial 
striae about 6 in *01 mm. 
Habitat — Santa Barbara County, California (Grove !). 
O. excavatus. Grev., Ralfs in Pritch. Inf , ’, p. 829, pi. viii. fig. 26. 
— Diam. from *1 to *255 mm. Surface with 1 to 3 rounded or 
subcuneate elevations, and alternate depressions around the centre, 
elsewhere subplain. Central rosette sometimes distinct. Markings 
hexagonal, increasing regularly outwards, but becoming somewhat 
smaller around the border ; near the centre 4, towards the border 
1J, at the border 2, in *01 mm., the central dots faint; secondary 
oblique decussating rows evident. Border striae 4 in ’01 mm. — 
Grun., Denk. Wien. Ah, 1884, p. 73. 
Habitat — Piscataway deposit (Dallas ! * Rae !) ; Newcastle 
deposit, Barbados (Rae !); Holland’s Cliff (Cleve); “ Artesian Well ” 
(Febiger). 
Var. genuina. Grun., ibid., p. 73. — Rarely elliptical. Diam. 
greater than that of the other vars., from *25 to *3 mm. Surface 
elevations and depressions 3. — G. excavatus, Grev., Sch., Atl., 
pi. lxv. fig. 1. 
Habitat. — Piscataway deposit (Dallas !* Rae ! Grunow, Deby !) ; 
Naparima (Grunow) ; Newcastle deposit, Barbados (Grunow, Rae !) ; 
Naparima, Trinidad (Firth ! Kinker !) ; Richmond, Ya. (Kitton) ; 
Rappahannock (Rogers !).* 
Var. quadrioeellata. Grun, ibid., p. 73. — Circular or roundly 
elliptical. Diam. T5 to T9 mm. Surface elevations and depres- 
sions 2. Central rosette inconspicuous. Markings more uniform ; 
towards the centre 4, towards the border 2, in *01 mm. Border 
striae, 6 in -01 mm. — C. diophthalmus, Cstr., Diat. Chall. Exped., 
p. 163, pi. xvi. fig. 4. 
* In the collection of Dr Greville. 
