SINUITBS BII.OBATIIS. 7 



3. Sinuites bilobatus (Sowerby). Plate I, fig. 8. 



1839. BeUerophon hiJohafiis, Sowerby, iu Murchison's Silurian System, p. 643, pi, xix, fig. 13. 



1848. BelUrophon hilohafus, Sowerby, Fc'russiic et, D'Orbigny, Hist. Nat. Cephal., vol. i, p. 188, pi. viii, 



figs. 2, 3. 

 1852. Bellero])lwn bilobatus, Sowerby, McCoy (pars), Syn. Brit. Pal. Foss. Woodw. Mus. fasc. ii, p. 308. 

 ? 1843. Bdleroplion gibbtts, Portloclc, Geol. Eep. Londoud., p. 398, pi. xxix, fig. 5. 



Specific Characters. — Shell siibglobose, outer wliorl completely embracing 

 all inner wliorls ; umbilicus minute or closed, subcentral, situated at a little 

 less than half the height of the shell ; dorsum and sides rounded. Mouth 

 transverse, wider than high, with prominent sharply rounded or almost bluntly 

 rectangular apertural lobes projecting forwards ; dorsal sinus U-shaped or bluntly 

 V-shaped, open, deep ; base of mouth scarcely expanded, not reflexed. Surface of 

 shell with fine, regular, transverse arched striae, distinct near mouth, concentric to 

 edges of lips, sharply arched forward on apertural lobes, well marked behind sinus 

 on dorsum and having a few stronger striae between them. Interior of shell with 

 faint traces of low, broad, transverse thickenings of shell, usually one or two 

 developed close to oral margins, most distinct on dorsum, obsolete on sides of whorl. 

 Dimensions. — (Type specimen [G850]). Height, about 85 mm. Thickness, 

 about 25 mm. 



Horizon. — Bala Series. 



Localities. — (1) Horderley ; Cynwyd; Corwen ? 



Remarks. — The above description is based on Sowerby's type [6850] in the 

 Jermyn Street Museum. The apertural lobes in this specimen have their anterior 

 ends imperfect, but judging from the curve of the striae must have been bluntly 

 rectangular or obtuse rather than broadly rounded. The ornament is rarely 

 preserved in the majority of specimens, but shows well in the type. 



So much confusion has arisen from an indiscriminate use of this specific name 

 that its strict limitation is necessary. Sowerby's original description, which is too 

 brief to be satisfactory, is as follows ; " Nearly globose, smooth ; aperture two- 

 lobed. Diameter 1^ inch, width of aperture 1 inch 3 lines." The first locality 

 which he gives is Horderley, and then follow Wistanstow, Welch Pool ; Michael- 

 wood Chase; Tortworth and Berwyns. Horderley is a Bala locality, and it is 

 highly doubtful if the Silurian localities, Tortworth and Michaelwood Chase, 

 should stand. The Horderley Ordovician shell will therefore be considered the 

 type of the species, which has been re-defined above. A large number of 

 specimens from this locality and its immediate neighbourhood have been examined, 

 but only some have been found to possess the typical characters ; many of those 

 identified by Salter and McCoy as S. hilohatus must be removed from association 

 with them. McCoy's^ definition is too comprehensive, as he included more than 

 one species under Sowerby's name. 



1 McCoy, ' Syn. Brit. Pal. Foss. Woodw. Mus.,' p. 808. 



