568 Proceedings of Royal Society of Edinburgh. [sess. 
fig. 14. — Diam. -05 mm. Surface flat. Centre indistinctly 
granular ; radial subuniform plications running from the centre to 
the border, and producing a wheel-like appearance. Markings 
minute, angular, 8 to 10 (?) in -01 mm.; radial rows between the 
plications evident ; secondary oblique rows distinct. Border 
relatively broad, sharply defined ; striae delicate, but evident. 
The appearance presented by the plications in the figure of 
Truan and Witt, are somewhat similar to the irregular clear areas 
found in Aulacodiscus acutus, Battray {Jour. Quek. Micr. Cl., 
vol. iv. ser. 2, p. 38, pi. iii. fig. 4. 
Habitat. — Jeremie marl (Truan and Witt). 
C. rhombicus , Grun. Van Heurk, Syn. Diat. Belg., pi. cxxix. 
fig. 3. — Diamond-shaped, angles obtuse, those at extremities of 
major axis the more acute. Major axis *0825, about 2J times 
minor. Surface showing a distinct elliptical central portion. 
Markings rounded, granular towards middle of central area, which 
elsewhere is hyaline, beyond this area rounded on a narrow zone ; 
on a distinct zone adjacent to the border more minute subpuncti- 
form, 10 in -01 mm.; rows beyond central area straight, secondary 
oblique rows faint. Apiculi distinct, at subequal wide intervals. 
Habitat . — Naparima deposit, Trinidad (Grove !). 
C. rex. Wallich, Jour. Roy. Micr. Soc. Lond ., 1879, p. 688. — 
Diam. 1*25 to 1*4 mm. Central space and rosette absent, but an 
indistinctly defined central area, with round isolated granules and 
hyaline interspaces, as well as distant irregular, somewhat curved 
large apiculi, evident. Markings on the central area without order, 
beyond this area round, forming straight closely disposed radial 
rows, 3 in '01 mm.; on the sides of the cylindrical valve the rows 
straight, and corresponding in position to those on flat surface of 
valve, but the markings smaller, 5 in *01 mm.; central papillae 
prominent ; a circular smooth space sometimes present at junction 
of terminal and lateral portions of cylindrical valve. — Sch., Atl., 
pi. cxiv. fig. 7 ; C. regins , Grun., Jour. Roy. Micr. Soc. Lond., 
1879, p. 688. 
This species was originally distributed under the name of C. rex. 
Habitat . — Bay of Bengal (Wallich, 1857 ; Kitton !) ; H.M.S. 
Challenger, Stat. 265, 2900 fathoms (Grunow); Nancoori (Cleve !). 
