48 OHDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



seiited ]:)y the Trenton species Gyrtolites nitidnJns, Ulrich,' and Bassler in 1915 

 (oj). cit., p. ^i()8) has adopted tlieir views. It" their generic name ])as therefore 

 any independent right to stand, the Latter species must be its type. 



1. Temnodiscus fletcheri, sp. nov. Plate IX, fig. 6. 



Specific Characters. — Shell lenticular, much compressed, acutely carinated ; com- 

 posed of few (2 — 3) whorls in contact but not overlapping, rapidly increasing in 

 size l)ut more in height than width, lanceolate in cross-section ; sides of outer 

 whorl very gently convex (? becoming flattened towards mouth), meeting at 

 very acute angle (15° — 20°) in carina. [Slit-band very narroAV.] Umbilicus open, 

 shallow, about one-third or one-fourth the maximum diameter of the shell, with 

 centre situated at about one-third its height ; umbilical edges subangular ; umbilical 

 slopes very short, vertical. Surface of whorls ornamented with regular, equi- 

 distant, narrow, transverse sublamellose ribs, nearly straight on sides but curving 

 back and becoming weaker and closer near carina, which they meet at 30°— 45" 

 but do not cross ; edges of ribs fimbriated ; interspaces slightly concave, crossed 

 by regular, equidistant, raised spiral lines, alternating in successive interspaces 

 and bearing closely-placed small granules ; near apertural margins the transverse 

 ribs and spiral lines become finer, less regular and more closely placed. 



Dimensions. — Height of shell about 14 mm.; height of mouth about 9 mm. 



Horizon. — Wenlock Shale. 



Localitij. — Dudley. 



Remarks. — Only the one specimen [27995] in the Jermyn Street Museum is 

 known to me, but it exhibits such marked characters as to merit a distinct specific 

 name. The mouth is not preserved, nor the slit-band. In shape, but not 

 precisely in ornamentation, the shell resembles T. pharetra (Lindstrom)' from the 

 Silurian of Gotland. The ornament, however, is more like that of some American 

 Ordovician species of Gonradella. 



2. Temnodiscus monilifer, sp. nov. Plate IX, fig. 7. 



Specific Characters. — Shell high, narrow, compressed, sharply angulated on 

 dorsum, cornuate, composed of 1 — 1^ free curved whorls with the umbilicus open 

 and perforated. Whorl very rapidly increasing in size to mouth, lanceolate in 

 cross-section, with gently convex sides meeting at an acute angle on the dorsum. 

 Mouth oblique, about 1^ times as high as wide. Slit-band flattened, becoming 

 narrower and completely (P) closed to form an acute keel in proximal part of 

 shell. Sides of whorl crossed by regular equidistant thick lamellce, gently arched 



1 Ulrich, ' Jouru. Cincinnati Soc. Nat. Hist.,' vol. ii (1897), p. 12. 



2 Lindstrom, op. cit., p. 83, pi. vi, figs. 39 — 51. 



