( 



E. S. Gobbold — Cambrian Hyolithidce from Hartshill. 153 



has uneven surfaces, indicating some amount of damage or com- 

 pression when freshly embedded in the matrix), ratio of axes (as 

 preserved) 1 to -5 ; aperture in two planes, dorsal lip projecting 

 a distance equal to one-third of the width (in the type-specimen it 

 is somewhat emarginate at the central line) ; surface marked near 

 dorsal lip with obvious lines of growth, elsewhere unknown ; 

 internal surface finely granular; dimensions, the complete shell (as 

 reconstructed) would be about 63 millimetres long and the width of 

 aperture (as preserved) is about 20 mm. 



Comparison with other species. — H. Willsi is only exceeded in size 

 by the Bohemian species H. giganteus, Novak l (Ordovician), and 

 II. maximus, Barrande (Middle Cambrian). 2 It is of about the same 

 length as H. princeps, Billings, 3 which, however, is much more 

 acuminate. 



II. Willsi agrees closely in some respects with H. excellens, 

 Billings, 4 from the Red Limestone of Trinity Bay, Smith's Sound, 

 Newfoundland. The Hartshill species has the same length, width, 

 rate of taper, and projection of dorsal lip, but its other characters 

 (convexity and surface marks) are unknown, and until further 

 material is available from Hartshill it seems best to describe it under 

 a new specific name. 



Horizon and Locality. — Lower Cambrian : the red sandy lime- 

 stone of Woodlands Quarry, Hartshill. 



Hyolithus {II.) cequilateralis, sp. nov. (PI. IV, Figs. 21, 22.) 



Type-specimens [25, 2]. 



Diagnosis. — Shell straight and tapering uniformly, so far as 

 known, at a rate of about 1 in 5 (equivalent apical angle about 12°), 

 apex not preserved. Section, dorsal face very gently convex, lateral 

 angles rounded, ventral face consisting of two surfaces which are 

 very slightly, if at all, more convex than the dorsal and are joined 

 by a rounded angle, the whole forming an equilateral triangle ; 

 aperture in two planes, dorsal lip projecting to a distance of about 

 one-quarter of the diameter, exterior not known. 



Remarks. — This species seems somewhat scarce; where the cross 

 section can be observed it is easily recognized, but otherwise it is 

 difficult to .distinguish it from some views of H. (0.) de Geeri, with 

 which it agrees in the rate of taper. It is near to H. Amerzcanus, 

 Billings, 5 which has a similar triangular section, but is not so 

 equilateral ; the projection of the dorsal lip also appears to correspond. 

 The exterior of that species is marked by transverse lines of growth 

 and longitudinal striae. 



Horizon and locality. — Lower Cambrian: the red sandy limestone 

 of Woodlands Quarry, Hartshill. 



1 K. Bohm. Gesell. der Wissensch., Folge vii, Band iv, No. 4, p. 19, pi. iv, 

 figs. 40-50, 1891. 



2 Sil. Syst. de Bohime, vol. iii, p. 5, pi. x, figs. 22-9, 1867. 



3 Can. Naturalist and Geologist, N.S., vol. vi, p. 216, 1872. 



4 Id., p. 471. 



6 Billings, op. cit., 1872, p. 215. 



