CYRTOLITES NODOSIJS. 25 



Dimensions. — Height of shell, about 32 mm.; Avidth of outer whorl near mouth, 

 about 10—12 mm. 



Horizon. — Lower Ordoviciau : Stinchar Limestone Group. 



Localities. — Craighead, Girvan ; (?) Minuntion, Ayrshire. 



Bemarhs. — Only internal casts of this species have been found; so that the 

 surface-ornament is unknown. From the shape of the cross-section, umbilical 

 edge, rate of increase in size of whorls, and general characters there is considerable 

 resemblance exhibited to C. sulplaiius, Ulrich,^ of the Trenton Formation and to 

 G. dilafatus U. and S.^ of the Black River Group. The types are in Mrs. Gray's 

 Collection. 



3. Cyrtolites nodosus (Salter). Plate V, figs. 1 — 2. 



1852. Bellerophon ornatus, Conrad, McCoy, Sju. Brit. Pal. Foss. Woodw. Mus., fasc. ii, p. 310. 

 1854. Belleroylion nodosus, Salter, Quart. Journ. Geol. Soc, vol. x, p. 73. 



1866. BeUerophon 7Wclosiis, Salter, Mem. Geol. Surv., vol. iii, p. 349, woodcut 15; ibid., 2ud edit. 

 (1881), p. 555. 



Specific Characters. — " Spire exposed, of about three rapidly increasing whorls 

 which are half as thick as broad, and of a subrhombic section ; the umbilical faces 

 rounded and much shorter than the other flattened ones. Sides marked by thick 

 raised [transverse] ridges which are not so broad as the intervening hollows ; they 

 are curved backward towards the flattened dorsal keel and nearly meet it, and 

 extend over the rounded edge of the steep umbilicus. The lines of growth are 

 beautifully regular, and they take a decided curve backward along with the ridges. 

 They are closely crenulate over the sides and back, and on the umbilical face 

 reticulate with each other. Their reticulated appearance arises from the close 

 approximation of the raised crenulate edges which thus decussate each other, and 

 become in some parts connected into a network. The ridges or plaits vary in their 

 distance from each other, but are very prominent." 



Dimensions. — i ii 



Height of shell . . . .26 mm. . 22 mm. 



Height of outer whorl at mouth . 14 „ . 12 „ 



Width of outer whorl at mouth . 12 ,, . 13 ,, 



Horizon. — Bala Series. 



Localities. — Soudley ; Onny River ; Horderley ; Llwyn-yr-hwch ; Maen Bras, 

 N. of Bala ; Cefn Llwydlo. 



Remarks. — The above is Salter's description of the species, and he points out 

 the characters by which G. ornatus, Conrad, differs from it. In the American 

 species the lines of growth are direct across, the umbilicus has a sharper edge, and 

 the plaits do not go beyond it. The localities which he gives are Teirw River, 



1 Ulrich and Scofield, op. cif., p. 862, pi. Ixii, figs. 40—44. 



2 Ibid., p. 865, pl. Ixii, figs. 20—23. 



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