558 Proceedings of Royal Society of Edinburgh. [sess. 
rows manifest. Border narrow ; striae evident, 6 to 8 in *01 mm. 
—(PI. II. fig. 13.) 
Habitat. — Oamarn deposit (Grove !). 
C. secernendus. Sch;, Atl., pi. cxiv. fig. 1. — Diam. -272 mm. 
Surface flat, towards the border convex. Central space absent; 
rosette distinct. Markings hexagonal, towards the border obtusely 
angular with long axes radial, pearly, decreasing gradually outwards; 
towards the centre 1J to 2, towards the border 2 to 2J, in •01 mm. 
Central papillae prominent, those on the markings near the border 
placed towards their central side ; secondary oblique decussating rows 
distinct, towards the border coarsely submoniliform, and separated 
by more distinct clear lines. Border narrow; striae 8 to 10 in *01 
mm. 
The appearance of the markings recall those of Aulacodiscus 
margaritaceus , var. Kinkeri. 
Habitat. — Maryland (Thum). 
C. moravicus, Grun. Sch., Atl., pi. cxiv. fig. 2. — Diam. *24 mm. 
Surface convex. Central space small ; rosette distinct. Markings 
hexagonal, obscurely punctate, towards the border submoniliform, 
increasing slightly outwards for some distance from the central space, 
again decreasing towards the border ; towards the centre 2 J, at the 
border 5, in. *01 mm.; central papillae faint, rows towards the 
border separated by evident clear lines ; secondary oblique 
decussating rows evident. Border narrow, hyaline. 
Distinguished from C. aster omphalus by the size and appearance 
of the markings. 
Habitat. — Hungarian marl (Thum). 
C. borealis. Bail., Amer. Jour. Sci., 1856, p. 3. — Diam. T5 to 
*25 mm. Surface slightly depressed at the centre, somewhat convex 
towards the border. Central rosette usually distinct, of 6 to 8 large 
areolae, sometimes subobsolete. Markings increasing regularly from 
the central rosette outwards ; towards the rosette 3 to 3 J, near the 
border 2, in. -01 mm.; central papillae distinct, the division lines 
composed of rounded granules; secondary oblique rows distinct. 
Border distinct, dark, with close irregular coarse striae. — Balfs in 
