214 



MR F. R. COWPER REED ON 



I. 



II. 



Til. 



15-0 



22-0 



21-0 mm 



8-5 



10-5 



1 1 -0 mm 



Dimensions : — 



Length of shell (to bend) . 

 Diameter of mouth 



Horizon and Locality. — Penkill Group, Penkill. 



Remarks. — The specimens are mostly rather crushed and imperfect, and the surface 

 ornamentation is rarely visible. The species which most resembles it is Ceratotheca 

 unguiformis, Novak, # from Stage Ee 1 in Bohemia, but the rate of tapering in the latter 

 is less rapid and the curvature of the shell begins nearer the apex ; the ornamentation 

 also is different. 



The inclusion of C. subuncata and the following species, C. balclatchiensis, in 

 the genus Ceratotheca, appears to me rather doubtful. However, it is impossible to 

 establish a new genus on such indifferent material, and it seems best to leave them 

 associated in it for the present. The resemblance of C. subuncata in general shape to 

 some species of Eccyliomphalus may be noted, and even Lindstrom's Euomphalus 

 gotlandicus t has a certain degree of similarity. 



II. 



III. 



25-0 



18-0 mm. 



9-0 



7 - mm. 



Ceratotheca ? balclatchiensis, sp. nov. (PI. III. figs. 1-3.) 



Shell conical, slightly curved ventralwards, rather rapidly tapering at about 1 in 3. 

 Cross-section subcircular to subelliptical. Ventral face strongly convex, rounded. 

 Lateral angles rounded, obsolete and indefinite. Dorsal face rather less convex than 

 ventral. Mouth straight or with margins slightly sinuous, at right angles to shell ; 

 no arched dorsal lip. Shell lustrous, corneous, thin, smooth, or with irregular faint 

 concentric growth-ridges and striae. 



Dimensions : — 



I. 

 Length ..... 21*5 

 Diameter at mouth . . . 8"0 



Horizon and Locality. — Balclatchie Group, Balclatchie. 



Remarks. — None of the specimens are very well preserved or complete, but it is an 

 abundant form at Balclatchie, and the numerous examples enable one to give a fairly 

 complete diagnosis. The affinities of this species are doubtful. It is much less com- 

 pressed dorso-ventrally than Hyolithes aduncus, Barr., from Stage E ; the lateral angles 

 are less evident and the shell tapers less rapidly. The thin, black, corneous nature of 

 the shell makes it doubtful if this organism is rightly referred to the Pteropoda at all, 

 but it hardly seems possible to regard it as annelidan in nature, and it may provision- 

 ally be referred to Ceratotheca. From its shape it looks as if it might be more correctly 

 placed with the Scaphopoda, but the nature of the shell is against this reference. 



* Novak, op. cit., p. 33, t. i. figs. 23, 24. 



t Lindktrum, Silur. Gastrop. Pterop. Gotland (1884), p. 139, pi. xiii. figs. 19-31. 



