166 Proceedings of the Boyal Physical Society. 



form amongst Mrs Gray's Turrilepas from Girvan. One of 

 these I propose to call 



Tiirrilepas Scotica, sp. nov,, Figs. 1 and 2. 



Sp. Chars. — General form elongately kite-shaped, curved ; 

 superior end curved and much attenuated, produced into a 

 fine needle-point ; inferior margin slightly convex, and a little 

 concave in the middle ; lateral margins, one convex through- 

 out the whole of its length, the other and opposite convex 

 in the lower part gradually becoming concave towards the 

 finely drawn out superior end ; lobation very indistinct, only 

 traceable through the curvature of the transverse stritie; a 

 median, ridge-like, sharp, and narrow keel, dividing the plate 

 into two sub-equal parts, passes from the central concavity of 

 the inferior margin to the sharp superior extremity ; the latter 

 is, in fact, formed by the extension of this central keel, the 

 plate on each side of it becoming abortive ; surface ornamented 

 with a very large number of transverse imbricating stride, 

 which in the central lobe are parallel to the inferior margin, 

 and on the lateral lobes are bent down parallel to the lateral 

 margins. 



Obs. — T. Scotica differs from the Dudley T. Wrightii, De 

 Koninck, in form, proportion, breadth of the central keel, in 

 the much augmented number of concentric striae, and par- 

 ticularly in the extended superior extremity. The same 

 characters also appear to separate it from all the species 

 described by M. Barrande. I feel confident that the present 

 form is a distinct type from any of the above, more especially 

 as one of Mrs Gray's specimens exhibits several of the plates 

 in close proximity to one another, all with the characteristic 

 attenuation of the superior extremity, and evidently belong- 

 ing to one individual. Unfortunately the state of preserva- 

 tion in this specimen is not sufficiently good to be worth 

 figuring. The other plates in the collection differ much from 

 T. Scotica in form, but notwithstanding the variation found 

 in the plates of any species of this genus, they will, I think, 

 prove to be different from T. Scotica. 



Log. and Horizon. — Balcletchie, south-east of Girvan, in 

 rocks of Silurian age ; exact horizon not yet determined. 



