212 MR F. R. COWPER REED ON 



Hyolithes (Orthotheca) subornatus, sp. nov. (PL II. figs. 13-15.) 



Shell slender, straight, slowly tapering at about 1 in 8, triangular in cross-section. 

 Ventral face strongly angulated at nearly a right angle, high, with strong median 

 longitudinal rib and 6-8 fine, straight, thread-like longitudinal lines on each side (with 

 2-3 very delicate ones between adjoining ones), and a strong marginal or supra-marginal 

 longitudinal rib near the lateral edge. Dorsal face apparently flat or slightly concave 

 and crossed by very fine transverse striae. Mouth straight. 



Horizon and Locality. — Whitehouse Group, Whitehouse Bay (and Shalloch Mill?). 



Remarks. — The peculiar ornamentation in this species distinguishes it from all 

 others in the Bala Beds. One specimen from Whitehouse Bay measures about 30 mm. 

 in length, but the tip is missing, so that its original length must have been about 35 

 mm., and its diameter at the mouth is about 4 mm. 



Some poorly preserved specimens from Shalloch Mill probably belong to this species, 

 but seem to taper rather more rapidly. 



Hyolithes (Orthotheca) thraivensis, sp. nov. (PI. II. figs. 16-23a.) 



Shell very slightly and regularly curved dorsalwards, or straight, gently tapering at 

 about 1 in 6 or 7, markedly triangular in cross-section, nearly as high as wide. Ventral 

 face strongly convex, high, more or less angulated. Dorsal face flat or slightly concave. 

 Lateral angles rounded, obtuse. Mouth straight, not oblique ; dorsal lip straight, not 

 arched. Surface of ventral face marked with 30-36 longitudinal equal or subequal 

 raised lines, separated by broader interspaces, and crossed by subequal, more closely 

 placed and more numerous but weaker raised lines, forming granules at the intersections, 

 and giving a cancellated appearance to the surface ; the 1 or 2 longitudinal lines on the 

 rounded lateral angles are rather stronger than the rest. Dorsal face crossed by straight 

 transverse lines similar to and continuous with those on the ventral face, but without 

 longitudinal lines. 



Dimensions : — 



I. II. 



Length about ..... 33*0 mm. 37 -0 mm. 



Width at mouth about .... 5*0 „ 6"0 ,, 



Horizon and Locality. — Drummuck Group (? including Starfish Bed), Thraive Glen. 



Remarks. — This beautifully ornamented species seems abundant in the Drummuck 

 Beds of Thraive Glen, and is usually well preserved and has the shell still attached. 

 //. (Orthotheca) trinucleorum, Holm,* maybe compared with this species, and it comes 

 from a homotaxial horizon. The ornamentation in H. (O.) thraivensis is coarser than 

 in //. (O.) snbexcavatus, and the shell tapers more rapidly, and is usually somewhat 

 curved. 



* Holm, op. cit., p. 67, t. v. figs. 79-87. 



