ORDOVICIAN AND SILURIAN BRACHIOPODA OF THE GIRVAN DISTRICT. 823 



Remarks. — This species differs from the typical Philhedra siluriana (Davidson) # of 

 the Wenlock Beds by its more elevated rounded capuliform shape and less central apex 

 and by its pustulate ornamentation. Several of the species of Philhedra described by 

 Von Huene t from the Baltic provinces have a general resemblance to it and some- 

 what similar ornamentation, but none seem very closely allied. It differs chiefly from 

 Crania setifera, Hall,} of the Niagara Group, by its more excentric and blunter apex. 



Philhedra ? penkillensis, sp. nov. 

 (Plate IV, fig. 34.) 



Shell subcircular, conical, less than half as high as wide ; apex excentric, situated 

 at about one-third the diameter of shell from posterior margin. Interior of upper 

 valve with two ? pairs of subcircular muscle-scars, the anterior pair subcentral and 

 large, posterior pair indistinct. Surface of shell ornamented with very fine closely 

 placed equal raised thread-like radial lines and a few concentric striae and growth- 

 ridges. Lower valve nearly flat. 



Dimensions. — Diameter about 5 '5 mm. ; height about 2 mm. 



Horizon.— Penkill Group. 



Locality. — Penkill. 



Remarks. — The single specimen of the upper valve with the shell preserved, on 

 which this species is founded, was labelled by Davidson as Discina sp. and marked 

 as drawn, but I cannot find out where it was figured. The position of this shell may 

 be either in the genus Philhedra or Pseudocrania, and its affinities may be with 

 Ph. Solaris (Eichwald).§ The muscle-scars are somewhat indistinct and uncertain, 

 but the anterior pair is fairly well seen in an internal cast. 



Philhedra Playfairi, sp. nov. 



(Plate IV, figs. 35, 36.) 



Shell subquadrate, widening anteriorly, slightly emarginate on anterior and 

 posterior borders. Upper valve convex, rounded ; apex obtuse, excentric, situated 

 nearer posterior than anterior margin ; posterior face short, steep. Interior of upper 

 valve with weak transversely oval posterior occlusors close to margin, and deeply 

 sunk subcentral circular anterior occlusors situated closer together, with narrow 

 longitudinal median ridge in depression between them ; strong lateral vascular sinus 

 on each side, extending round in front of anterior occlusors and nearly meeting in 

 middle and giving off to margins short radiating lateral branches. Surface of shell 

 ornamented with thin sublamellose concentric growth-ridges somewhat irregular, 

 and bearing small sub-equidistant pustules. 



* Davidson, Mon. Brit. Foss. Brach., vol. iii, pr,. vii, p. 82, pi. viii, figs. 19, 20. 

 t Von Huene, op. rib., pp. 297-315. 



% Hall, 11th Ann. Rep. State Geol. Indiana, 1882, p. 283, pi. 21, figs. 8-10. 

 § Von Huene, op. cit., p. 308, t. iv, figs. 23, 24. 



