44 ORDOVICIAN AND SILURIAN BELLEROPHONTACE A.. 



rest but not producing prominent ridges as in B. arfoneiisis ; nor do they form 

 conspicuous ridges on the band as in that species. Umbilicus open, broad, deep." 



The only two specimens (nos. 28008, 28009) of this species are in the Jermyn 

 Street Museum and correspond to Salter's figures ; but they are fragmentary, the 

 larger specimen (28009) showing the dorsum of the terminal portion of the outer 

 whorl with the surface ornament, slit-band, dorsal sinus, and part of the lip. The 

 other specimen is a less perfect but larger portion of a smaller shell. 



This species appears to belong to the genus Tetranota as defined by Uliich 

 and Scofield, and it seems to be the only English species so far discovered. Its 

 nearest ally appears to be T. obsoleta, Ulr. & Scof.,^ which occurs in several 

 Ordovician beds in Minnesota. 



Genn.s CONRADELLA, Ulrich and Scofield. 



Generic Cliaracteys. — Shell coiled symmetrically ; whorls in contact but scarcely 

 overlapping, enlarging gradually, strongly keeled dorsally. Umbilicus open. 

 Aperture oval or subcordiform, widest in middle or below, entire, with margins 

 abruptly expanded and inner lip reflexed, without dorsal sinus or callosities, but 

 having long narrow median dorsal slit with raised edges extending about half the 

 length of outer whorl and followed by elevated slit-band. Surface of shell 

 ornamented with imbricating transverse lamellge, having their edges often plicated 

 so as to form revolving ridges; fine transverse growth-lines generally present. 



The type of this genus is G. obliqua, Ulrich and Scofield,^ from the Black 

 River Group. A species ascribed to this genus has been described by the author^ 

 from the Slade Beds of the Haverfordwest area, but otherwise it does not seem to 

 have been recorded from the British Isles. Perner (op. cit., p. 158) recognises one 

 species from Etage Ee in Bohemia. Ulrich and Scofield's definition of the genus 

 is here strictly followed. Bassler* prefers to use the name Vhr<t(j]iwlileii, Conrad, 

 1838, in place of Gonradella, but the type of Phraijmolites is not the same species, 

 being P. compressus, Conrad/ from the Trenton Formation. 



1. Conradella girvanensis, sp. nov. Plate IX, fig. 1. 



Specific Gharacfers. — Shell high, subdiscoidal, composed of 3—4 subtriangular 

 rounded whorls, higher than wide. Umbilicus wide, more than one-third the 



1 Ulrich and Scofield, oj). cit., p. 880, pi. Ixv, figs. 19—23. 



2 TJlrich and Scofield, o}). cit., pp. 851, 904, 906, pi. Ixvii, figs. 1 — 6. 



3 Keed, ' Geol. Mag.' [5], vol. iii (19U6), p. 367, pi. xx, figs. 5, 5 a, J). 



* Bassler, ' Bibliogv. Index Amer. Ordov. Silur. Foss.,' vol. ii, p. 971 (Bull. 92, U.S. Nat. Mus., 

 1915). 



^ Conrad, ' 2ud Aun. Kep. New York Geol. Surv.,' 1838, p. 119 ; Hall, ' Pal. New York,' vol i 

 1847), p. 188, pi. xIa, figs. 2 a — ■/ [Cyrlulites comj)ressus]. 



