824 DR F. R. C. REED ON THE 



Dimensions. — Length, 12'0 mm. ; width (maximum), 15'0 mm. 



Horizon. — Balclatchie Group. 



Locality. — Dow Hill. 



Remarks. — Only one internal cast of the upper valve and a portion of the 

 impression of the shell of the same specimen are available. The internal characters 

 suggest a relationship to Ph. rivulosa (Kutorga),* but the ornamentation of the 

 surface is more like Pseudocrania petropolitana (Pander), f The interior is much 

 like Crania Crofti, Dav.,| from the Bala beds of Wales. This species is dedicated to 

 the famous Scotch professor, John Playfair. 



Philhedra siluriana (Davidson). 

 (Plate IV, fig. 37.) 



1866. Crania siluriana, Davidson, Mon. Brit. Foss. Brack., vol. iii, pt. vii, p. 82, pi. viii, figs. 19, 20. 

 1883. Crania siluriana, Davidson (pars), op. cit., vol. v, Silur. SuppL, p. 215, pi. xvii, figs. 49, 50 

 (non figs. 51-53). 



This species was recorded by Davidson from Woodland Point and Mulloch Hill, 

 but nearly all those from the latter locality seem to belong to the species here 

 described as Ph. mullochensis. The typical Ph. siluriana is much flatter, more 

 depressed, and the ornamentation consists only of concentric growth-ridges. Hall's § 

 Crania siluriana from the Niagara Group is probably identical in this restricted 

 sense. In a few examples from Woodland Point some of the muscle-scars can be 

 distinguished, and it is seen that the anterior occlusors are circular and larger than 

 the posterior ones (which are very faint) and situated their own diameter apart. 

 Von Huene || refers this species to the genus Philhedra. 



Horizons— (l) Saugh Hill Group ; (2) ? Mulloch Hill Group. 



Localities.— (I) Woodland Point; (2) ? Mulloch Hill. 



Philhedra sp. 

 (Plate IV, fig. 38.) 



One internal cast of the upper valve of a species of Philhedra from the Starfish 

 Bed occurs in the British Museum, but it cannot be referred to the above-described 

 species Ph. drummuckensis from the same horizon. 



The shell is conical, and semi-elliptical in shape, being wider than long ; the apex is 



situated nearer the posterior than the anterior end ; a pair of large subcircular anterior 



occlusors lie at about half their diameter apart a little behind the apex, and the 



much smaller posterior adductors are situated submarginally and relatively further 



apart from each other, but the centres of the pairs of muscle-scars lie on parallel 



* Von Huene, op. cit., p. 300, pi. iv, figs. 8-16. t Von Huene, op. cit., p. 231, pi. i, figs. 4-14. 



I Davidson, Mon. Brit. Foss. Brack., vol. v, Silur. Suppl, v, p. 215, pi. xvii, figs. 54-56. 



$ Hat.l, Trans. Alba7iy Instit., vol. iv, p. 208 (1863); id., 11th Ann. Report State Geol. Indiana, 1882, p. 282, 

 pi. 21, figs. 3-7 ; Beecher and Clarke, Mem. New York Slate Mus., i, 1889, p. 13, pi. 1, figs. 1, 2. 

 || Von Huene, op. cit., p. 217. 



