BRONTEUS CRAIGENSIS. 89 



luiinirl-x. — Nicholson and Ltheridge described the transverse wrinkles on the 

 axis of the pygidium as axial rings, but there is only one true ring on the front of 

 the axis, the wrinkles or imbricating stria? being of the same nature as the 

 concentric stria? on the lateral lobes. The affinities of this form have been 

 discussed by the same authors, but it seems to me that the pygidium is allied to 

 that of B. partschi, Barr., 1 from Et. E in Bohemia. The characters of the head- 

 shield and glabella (which occur at Penkill in the closest association with the 

 pygidia), also bear some resemblance to those of the same species so far as 

 they are known. Toll 2 has described Bronteus andersoni from the Silurian 

 beds of Kotelny, one of the New Siberian Islands; but, judging from the figure 

 and description, it appears to me somewhat doubtful whether his specimens really 

 belong to the Girvan species. 



Collections. — Mrs. Gray (f. M.) ; Museum of Practical Geology ; Edinburgh 

 Museum; Hunterian Museum, Glasgow. 



Horizons and Localities. — -Saugli Hill Group (M. Llandovery) : Woodland Point. 

 Camregan Group (IT. Llandovery) : Bargany Pond Burn ; Penwhapple Glen. 

 Penkill Group (Tarannon) : Penkill. 



2. Bronteus craigensis, sp. nov. Plate XII, figs. 12, 13. 



1899. Bronteus Mbemicus, Mem. G-eol. Surv., Silur. Rocks Brit., Scotland, vol. i, pp. 671, o7±. 



Specific Characters. — Pygidium sub-semicircular, very slightly convex. Axis 

 short, conical, feebly convex, broader than long, about one third the length of 

 the pygidium and less than one fourth its width ; consisting of one or two 

 faintly-marked rings at the front end and of a triangular piece behind. Axial 

 furrows very faint, converging at about 80°, but obsolete at posterior end of axis. 

 Lateral lobes composed of six pairs of simple radiating, slightly raised pleura?, 

 curved gently backwards, and separated by distinct but shallow interpleural 

 furrows, dying out near margin. Sixth pair of pleura? very indistinctly defined. 

 Broad post-axial piece, apparently composed of the completely fused seventh pair 

 of pleura?, but without any trace of an interpleural furrow. 

 Dimensions. — 



Length of pygidium .... 18*0 mm. 

 Width of „ . . . 29-0 „ 



Length of axis .... &b ., 



Width of „ . • • .7-0 „ 



Remarks. — There are several pygidia of this form from Craighead in .Mrs. 



1 Barraudo, ' Syst. Sil. Boherne,' vol. i, p. 870, pi. xlvi, figs. 19 — 31. 



- Toll, 'Mem. Acad. Imper. Sci., St. Petersburg, vol. xxxvii (1890), No. 3, p. 39, pi. iii, tig. 5. 



12 



