136 TRILOBITES OF GIRVAN. 



close to axis and near outer ends of pleurae. The hypostome of Calymene which 

 occurs in the Starfish Bed and may be referred to this variety of G. blumenhachi, 

 possesses a few features differing from the typical form. It is wider in front, 

 narrower behind, and altogether more elongate in shape. The posterior margin is 

 more deeply emarginate and the posterior alae are not so far back. The body is 

 more compressed and elevated, rising regularly to the median tubercle, and the 

 band across the posterior end of the body is only faintly defined. 



In spite of the considerable differences in the glabellar lobes and other parts, 

 it seems preferable to regard this form as only a variety of G. blumenhachi, though 

 without doubt it is a well-marked one deserving a distinctive name. The designa- 

 tion G. blumenhachi var. drummuckensis may be accordingly suggested. 



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

 Museum ; Woodwardian [Sedgwick] Museum ; Hunterian Museum. 



Horizon and Localities. — Drummuck Group (IJ. Bala) : Drummuck ; Thraive 

 Glen (Starfish Bed). 



'2. Calymene cambrensis, Salter, 1865. Plate XVII, fig. 16. 



1848. Calymene brevicapitata, Salter, Mem. G-eol. Surv., vol. ii, pt. i, pi. xi, fig. 3 (? figs. 4, 5). 



1854. Calymene brevicapitata, M'Coy, Synops. Pal. Foss. Woodw. Mus., p. 165, pi. i f, figs. 4, 5 (non 



fig. 6). 

 1865. Calymene blumenhachi, var. cambrensis, Salter, Mein. Geol. Surv., vol. iii, pi. xvii, figs. 13, 14. 

 1865. Calymene cambrensis, Salter, Mon. Brit. Trilob., p. 98, pi. ix, figs. 12—14. 

 1873. Calymene cambrensis, Salter, Cat. Camb. Silur. Foss. Woodw. Mus., p. 33. 

 1877. Calymene cambrensis, Woodward, Cat. Brit. Foss. Crust., p. 28. 

 1879. Calymene blumenhachi, Nicholson and Etheridge (e. p.), Mon. Silur. Foss. Girvan, fasc. ii, 



p. 140 (non pi. x, figs. 2 — 6). 



Remarks. — There exists, unfortunately, a state of great confusion and uncertainty 

 in connection with most of the British Ordovician species of Calymene. Pompecki 1 

 has recently attempted to introduce some definiteness into our conceptions of the 

 various species, but perhaps not with complete success, and this is not the place for 

 a thorough revision of the species. Nicholson and Etheridge put all the Girvan 

 Ordovician representatives of the genus into the species G. blumenhachi, as above 

 recorded, and enlarged the synonymy of that species accordingly, but this is a 

 course which I cannot consider justified. Only the Silurian forms of Calymene in 

 the Girvan area may, in my opinion, be attributed to the true C. blumenhachi, and 

 they are distinct from the Ordovician, amongst which may be recognised in this 

 area three separate species — C. cambrensis, Salter, C. planimarginata, sp. nov., 

 mid the Drummuck variety of C. blumenhachi which has been above described. 



The species C. cambrensis is characterised by its glabella being parabolic, short 

 and broad, with convex sides, not contracted in front of the basal lobes ; by its three 

 1 Pompecki, ' Neues Jahrb. fur Miner.,' 1898, vol. i, p. 187. 



