﻿BEITISH FOSSIL CEPHALOPODA. 143 



familiar to him. Barrande, however, makes no reference to M'Coy 's species, but 

 figures and describes 0. lancea with identical characters, and the distinctions relied 

 on to separate from the latter 0. lentum and 0. potens would not be sufficient for 

 me. The example referred by M'Coy to 0. acuarium, Miinster, may very probably 

 be a young form of this species. Its rate of increase is 1 in 15. The septa are § 

 the diameter apart, and the siphuncle is f along the diameter, and appears as a 

 continuous tube. It therefore has a far greater rate of increase than the species 

 referred to by M'Coy, and a non-central siphuncle. The imperfect specimen named 

 by Portlock Koleoceras speciosum may probably belong to the present species. 



Distribution. — In the Bala Beds of Glenwhapple, Ayrshire (10); in the 

 Coniston Limestone, Troutbeck (1) ; in Lower Silurian beds of Desertcreat (1), 

 Clare (1), Portraine (1), Waterford (1), Cong (1), Blackwater Bridge (1), and 

 possibly two species from Kirkcudbright (4). 



It is also recorded by Geikie, from Bala Beds at Carrick ; by Davies, at Llechwyd, 

 Nant Iorweth, and Glynceirog ; by Geikie, from the Coniston Limestone, Keisley ; 

 and from Craig Head, in the Catalogue of Western Scottish Fossils. 



Orthoceras audax, Salter, PI. XII. fig. 8. 

 1866. Orthoceras audax, Salter, 'Memoirs of the Geological Survey,' vol. iii. pi. 24, fig. 7, p. 357. 



Type. — Section nearly circular, the diameters in the ratio of 8 to 7 ; rate of 

 increase 1 in 6. The whole is septate, and no external ornaments are visible. 

 The septa are slightly undulating, rising on one of the narrow sides ; their 

 convexity is very slight, and their distance a little more than -f the longer diameter. 

 The siphuncle is not seen in this specimen. Greatest diameter, § inch ; length, 

 nearly 2 inches. From the Bala Beds of Rhiwlas Bala. In the Museum of 

 Practical Geology. 



General Description. — In some examples there is an appearance of squareness 

 about the section, and the diameters are always unequal : when most so, they are in 

 the ratio of 11 to 9. The rate of increase is 1 in 5 to 1 in 7. No body-chamber has 

 been seen. The septa undulate to an amount of 3^°, being highest on the narrow 

 side ; they are very slightly convex or almost flat, and most are \ to -§- the diameter 

 apart, but they may be more remote. The siphuncle is very slightly excentric on 

 the long axis towards that side to which the septa rise ; its diameter is small. 

 The largest fragment has a diameter of 1 inch. 



Relations. — Salter states that the specimens referred by M'Coy to 0. gregarium 

 (Sow.), which come from the Bala Limestone of the Chair of Kildare, belong to this 

 species; but those preserved in the Museum of Practical Geology show very 



