208 MR F. R. COWPER REED ON 



above mentioned. It is probable that Salter* refers to H. immemor in recording 

 //. reversa (Salter) from the South of Scotland. In the latter species, originally 

 described from North Wales,t there is no mention of a tapering chambered apex, but it 

 seems closely allied in other respects. Eichwald (op. cit., p. 1045) believed that the 

 Russian species, H. acutus, Eichw., which Holm J has fully described, from the 

 Orthoceras Limestone, was a close ally of H. reversa. 



Amongst other Scandinavian species, it may be remarked that the ribbing of the 

 ventral face of H. scalprum, Holm,§ is somewhat similar. 



Probably certain small opercula (PI. II. fig. 1) occurring in the same beds at 

 Ardmillan are referable to this species. This type of operculum is subcircular in shape, 

 conical, with an elevated excentrie apex situated close to the ventral margin ; the 

 ventral face is triangular, short, flattened, more or less inclined to the general surface, 

 and has a small median prominent fold below the apex, traversing it and extending 

 to the margin. The general or dorsal surface of the operculum slopes down regularly 

 from the apex and has one distinct regular concentric groove near the margin, and 

 fine concentric strise above and below. In casts, two short, shallow, broad radial 

 grooves, diverging from the apex at about 80° and widening outwards, traverse the 

 dorsal portion of the shell, but do not extend more than two-thirds of the distance to 

 the margin. These indicate muscular attachments, and correspond to those represented 

 by Barrande || in opercula from Stage D in Bohemia. 



Hyolithes multipunctatus, sp. nov. (PI. II. figs. 2-26.) 



Shell straight, gently tapering at about 1 in 6-7. Dorsal and ventral faces gently 

 convex, the ventral side rather more convex than the dorsal. Lateral edges sharp, acute. 

 Mouth oblique ; dorsal lip slightly arched and swollen at margin. Surface of shell crossed 

 by weak growth -ridges at irregular distances and by finer growth-lines and strise, and 

 covered with small, round, shallow pits, situated at about two to three times their 

 diameter apart. 



Dimensions : — 



Length (of broken fragment of shell) . . . 45 "0 mm. 



Width of mouth ....... 16-0 „ 



Horizon and Locality. — Balclatchie Group, Ardmillan. 



Remarks. — Only one broken specimen with the impression of its exterior is known, 

 but this, luckily, has the mouth and ornamentation well preserved. The latter feature 

 is peculiar, and does not appear to be of a secondary origin. It easily marks it off from 

 other allied species, such as H. asteroideus. 



* Salter, Mem. Geol. Surv., vol. iii., 1866, p. 353, and woodcut 14, fig. 6, on p. 347. 



t Salter, in Murchison's Siluria, 2nd edit., p. 550, foss. 10, fig. 21. 



\ Holm, op. cit., p. 99, t. ii. figs. 29-36, t. vi. fig. 23. 



§ Holm, op. cit., p. 96, t. ii. figs. 46-50. 



|| Barrande, op. cit., pp. 95-97, pi. xiii. figs. a-e. 



