54 ORDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



The slit-baud forms an elevated keel with a flat top, on each side bordered by 

 a fine line and wavy with the minute and delicate lines of growth. Whorls four 

 and a-half, regularly increasing in width, twice as large as high and consequently 

 not so narrow as in B. sphsera. Shell thick and as common in the genus [at] 

 thickest around the umbilicus and at the inferior corners of the aperture. The 

 last whorl, when seen from the side, is straight or only faintly curved, and its 

 aperturaJ and dorsal contours are nearly parallel. . . . The inferior corners 

 of the aperture near the umbilicus where the shell is [at] thickest, are rounded 

 or cylindrical, and completely hide the umbilicus, which in young specimens is 

 open " (Lindstrom). 



There are several shells in the Sedgwick Museum labelled by Salter Belleruphon 

 dilatatus which completely agree in all essentials with Liudstrom's />. globulus. 

 The subquadrate semi-elliptical shape of the whorls, the straightening of the last 

 whorl, the high expanded mouth, the narrow raised slit-band flattened at the top, 

 are just as Lindstrom describes and figures. The transverse strire on the shell, 

 though they meet the slit-band at an angle between 35 and 45° as in the Swedish 

 form, are not always extremely fine and densely packed, for they may be rather 

 irregular in strength, though fine on the whole. One specimen (a/877) from 

 the Wenlock Limestone, Dudley, in the Sedgwick Museum, has the slit-band, shell 

 and surface ornament well preserved, and they agree precisely with Liudstrom's 

 figures and descriptions. Internal casts of the species are, however, as a rule 

 only preserved, and these have frequently been labelled 11. wenlockensis. But 

 //. globulus is less globose in shape, the whorls are relatively higher, the 

 cross-section is semi- elliptical and not so transverse. The sides tend to be 

 somewhat flattened, and the dorsum is only distinctly angulated towards the 

 mouth. The shape of the whorls, degree of convexity of the dorsum and 

 expansion of the mouth vary somewhat in this species, as Lindstrom himself has 

 pointed out. 



Dimensions. — Height of shell, c. 43 mm. ; width of mouth, c. 50 mm. 



Horizons. — (1) Wenlock Limestone; (2) Lower Ludlow; (3) Upper Ludlow P 



Localities. — (1) Dudley; Dbrmington Wood, Woolhope; (2) Ledbury; Dudley; 

 (3) Kendal [28102, 2810:]] (Jermyn Street Museum). 



2. Bellerophon ledburiensis, sp. now Plate IX, fig. 14. 



1878. Bellerophon wenlockensis, Sowerby, Salter, Cat. Camb. Silur. Foss., Mus. Pract. G-eol., p. 113. 



Specific Characters.-^-SheW globose, involute, outer whorl completely enveloping 

 inner whorls and slowly increasing in size to mouth. Umbilicus closed, with stout 

 rod-like callosity projecting from it. Whorl transverse, more than twice as wide 

 as high; dorsum broad, rounded, gently convex; sides rounded, inflated. Slit- 



