I. 



II. 



9-5 



15*5 mm. 



11-5 



21-0 mm. 



218 MR F. R. COWPER REED ON 



Pterotheca multidecorata, sp. nov. (PI. III. figs. 14-16.) 



Shell semi-elliptical, with long, strongly arched apertural margin and short postero- 

 lateral margins meeting at apex at wide angle (about 130°-150°); apertural margin 

 narrowly and not deeply, but acutely, emarginate in centre. Surface of shell gently 

 convex ; median fold high, angulated, acute, with narrow raised keel, increasing 

 gradually in width and somewhat in height to anterior margin, where it ends in the 

 median notch ; lateral folds low, rounded, curving slightly outwards and projecting as 

 rounded lobes on margin, well marked off from median ridge and from lateral portions 

 of shell, which form broader and lower outer rounded folds ; the grooves separating 

 these outer from the inner lateral folds diverge at rather less than 45°. Surface of 

 shell marked (l) by a few concentric corrugations and striae bending back acutely at a 

 re-entrant angle of 45°-50° on median fold, and (2) by fine radial striae, slightly wavy, 

 and increasing in number towards the margin, containing along them a row of closely 

 set minute punctae. Internal septa indistinct, thin, gently curved, less than the length 

 of shell, diverging from apex at about 30°-45°, and running in outer lateral grooves. 



Dimensions :■ — 



Length ...... 



Width ...... 



Horizon and Locality. — Penkill Group, Penkill. 



Remarks. — The ornamentation of this shell easily marks it off from all the other 

 species, somewhat resembling that in the brachiopod Porambonites. The two pairs 

 of lateral folds and shape of the shell are additional distinguishing features. Pt. 

 avirostris, Salter (MS.), from the Upper Llandovery of Bog Mine, Shelve, and Damery 

 Bridge, Tortworth, is only known as internal casts. It is almost circular in outline, and 

 does not show clearly two pairs of lateral folds, but the high angulated narrow keel and 

 the small angle of divergence between the internal septa constitute points of resemblance 

 between it and Pt. multidecorata which are worthy of notice. 



Pterotheca simplex, sp. nov. (PI. III. figs. 17, 17a.) 



Shell small, transversely semi-elliptical, with strongly arched apertural margin. 

 Surface gently convex, with one broad, slightly elevated subangular median fold, 

 increasing rapidly in width from the beak to the apertural margin, where it projects 

 slightly and has a width equal to nearly half the shell ; it is bounded laterally by 

 weakly impressed shallow grooves, curving gently outwards to margin, and diverging 

 from apex at about 45°. Lateral folds obsolete. Concentric corrugations and striae few 

 and faint, strongest near apex. 



Dimensions : — 



Length . . . . . . . . 5 25 mm. 



Width . . . . 7-0 „ 



