8 ORDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



The true S. bilohatus is more allied to the species S. suhrectangularis, sp. nov., 

 from Girvan in respect of the shape of the apertural lobes than to 8. sotidlei/eusis, 

 sp. nov., which has been frequently confused with it. But it differs from the 

 Scottish form in the absence of internal thickenings of the same strength, and in 

 possessing a more rounded dorsum. 



In the shell from the Ordovician of Spain attributed by De VerneuiP to 

 Sowerby's 8. hilobatus the presence of two or three concentric internal transverse 

 thickenings is represented in the figure and especially noticed in the description, 

 though owing to the fossil being in the condition of an internal cast they appear 

 as grooves instead of ridges, and are described as such. 



4. Sinuites crypticus, Reed. 



1906. Belleroj-)hon {Sinuites) crypticus. Reed, Geol. Mag. [5], vol. iii, p. 363, pi. xx, figs. 12 — 14. 



8i)ecific Characters. — Shell closely coiled, subglobose, sides somewhat flattened, 

 greatest thickness at uml)ilicus, back narrowly rounded ; outer whorl com- 

 pletely embracing and hiding inner whorls and increasing rather rapidly in 

 size to mouth ; umbilicus minute (exposed in casts) ; section of whorls semi- 

 elliptical to parabolic ; aperture higher than wide, not expanded laterally ; outer 

 lip thin ; inner lip more or less reflexed and thickened ; dorsal sinus moderately 

 deep, broadly V-shaped; apertural lobes gently rounded below, but angulated 

 obtusely at origin of sinus, where the margin is rather suddenly and sharply 

 curved inwards. Surface of shell ornamented with rather strong concentric 

 growth-lines and ridges on apertural lobes, and generally with one rather strong 

 internal thickening a little inside margin of mouth ; general surface of shell orna- 

 mented with a minute regular cancellation composed of equal-sized, fine revolving 

 striae closely placed and crossed by similar transverse, slightly flexuous striae. 



Dimensions. — Height (average) about 20 mm., diameter (average) about 

 8 — 10 mm. 



The affinities of this shell were discussed by me in the original description of 

 the species, and it only remains to be added that the Girvan form 8inuites 

 discoides, sp. nov., appears to resemble it somewhat in ornamentation, and that 

 a similar cancellation of the surface is found in 8. reticidatus, Perner.^ The 

 holotype is in the Sedgwick Museum. 



Horizons. ^{l) Redhill Beds; (2) Slade Beds (Upper Ordovician). 



Localities. — (1 ) Prendergast Place and Lane ; (2) Lane near Crundale ; Robes- 

 ton Wathen. 



BemarJcs. — The internal surface of the shell on and near the concentric thickening 

 is covered densely with small granules showing as pits in internal casts. 



1 De Verneuil, ' Bull. Soc. Gcol. Frauce ' [2], vol. xii (1855), p. 984, pi. xxvii, fig. 1. 



2 Perner, op. cit., p. 64, pi. Ivi, figs. 42, 43 ; pi. Ixxxvi, figs. 33, 34 ; text-figs. 37 — 40. 



