522 
Proceedings of Royal Society of Edinburgh. [sess. 
adjacent to border. — Cestodiscus Baileyi , H. L. Sm., Diat. Spec. 
Typ ., No. 67. 
This species was first collected by Lieut. Williamson ( Explor . 
and Surveys for Railroad Route from Mississippi River to Pacific 
Ocean, vol. vi. pt. 2, “Geology,” chap. iv.). Prof. H. L. Smith, in 
his remarks on the species, first throws doubt on the validity of the 
genus Cestodiscus. 
Habitat. — Lost River, lower Klamath Lake, Oregon fossil 
(H. L. Smith !). 
C. fragilissimus, Grun,, in Van Heurck, Syn. Diat. Belg., pi. 
cxxviii. fig. 4. — Diam. *3165 mm. Central space minute, indistinct, 
rounded. Markings minute, 12 in *01 mm.; secondary oblique 
rows manifest ; apiculi distinct, scattered at wide unequal intervals, 
most crowded towards the border. Border narrow, hyaline. — Ethmo- 
discus convexus, Cstr., Diat. Chall. Exped ., 1886, p. 167, pi. iii. 
fig. 9. 
Habitat. — Arafura Sea (Yan Heurck, Castracane !). 
C. asteroides. Tru. and Witt, Jeremie Diat., p. 13, pi. iii. fig. 2. 
— Diam. T5 to 2 mm. Surface usually showing a circlet of six to 
twelve small shallow depressions at a distance of J to \ of the 
radius from the centre. Central space absent. Markings hexagonal, 
on a small central area 2 to 2\ in ‘01 mm., decreasing somewhat 
suddenly at about i of the radius to 3 or 3J, thence increasing 
gradually outwards to 1J in -01 mm., again becoming somewhat 
smaller at the border. Central papillse distinct ; secondary oblique, 
curved, decussating rows manifest. Border narrow. 
In Maryland specimens the shallow depressions are not found. 
Habitat. — Monte Gubbio (Grove !) ; Jeremie deposit (Truan and 
Witt !) ; Cove, Calvert County, Maryland (Greville !) ; South 
Naparima, Trinidad (Greville !) ; Nottingham deposit, Maryland 
(Johnson !) ; * Rappahannock, Ya (Greville !). 
C. lunatus. Grove MS. — Diam. ’09 to T5 mm. Central space 
minute ; a rosette frequently distinct, occasionally subobsolete. 
Surface with an evident lunate unilateral depression, its long axis 
at right angles and subequal to or somewhat longer than the radius, 
* In the collection of Dr Greville. 
