LOWER PALEOZOIC HYOLITHID^E FROM GIRVAN. 213 



Hyolithes (Orthotheca) thraivensis, var. granuliferus. (PL II. figs. 24, 25.) 



Shell straight, triangular, slowly tapering at about 1 in 6. Ventral face high, 

 angulated, its sides meeting at about a right angle. Dorsal face slightly concave. 

 Lateral angles obtuse, rounded. Mouth straight. Ventral face bearing one strong 

 median raised longitudinal line along ridge and 6-8 finer raised lines on each side, each 

 line bearing a single row of small equidistant tubercles. The longitudinal lines are not 

 all of equal strength or at equal distances ; some are finer than others and are not 

 continued to the point, only extending about half or two-thirds the length of the shell ; 

 the interspaces between the lines are wide, and very delicate transverse lines cross them. 

 The rounded lateral angles bear several similar longitudinal lines, but the dorsal face 

 seems devoid of them, and only shows very faint transverse strise. 



Horizon and Locality. — Drummuck Group, Thraive Glen. 



Remarks. — The one internal cast and external impression on which this variety is 

 based differ from the typical form by the granules on the longitudinal lines being 

 fewer and so much larger as to be w T orthy of the designation of tubercles. The longi- 

 tudinal lines also are fewer and less regular, and the concentric strise much finer and 

 fewer. The fragment measures about 1175 mm. in length, with an apertural diameter 

 of about 4 '25 mm. 



Hyolithes (Orthotheca?), sp. ind. 



An elongated, narrow, slowly tapering species from Penkill is represented by one 

 poor and imperfect specimen in the Hunterian Museum, Glasgow. The fragment 

 measures 32 mm. in length, but the tip is broken off; at its broader end it measures 

 3 "25 mm. in width ; its true rate of tapering is about 1 in 11. The impression of the 

 one face preserved shows that this face ( ? the dorsal) must have been gently convex, 

 and there are traces of faint transverse, scarcely arched striae running across it. No 

 other features can be detected. 



Genus Ceratotheca, Novak, 1891. 



Ceratotheca ? subuncata, sp. nov. (PI. II. figs. 26-28.) 



Shell cornuate, strongly curved back at about half its length, and thence rather 

 rapidly tapering to point, the curvature being such that the posterior part of the shell 

 is bent back in a regular, nearly semicircular curve, so that the apical extremity lies at 

 about two-thirds to three-fourths the length of the shell. Section of shell subcircular 

 or elliptical. Mouth at right angles to shell, not oblique ; margin of mouth slightly 

 sinuous. Shell thin ; surface ornamented with very fine concentric growth-striae 

 and with very delicate closely placed longitudinal striae (observable near mouth), which 

 on crossing the transverse strise are raised into minute granules. 



