STNITITES SOUDLEYBNSIS. 13 



10. Sinuites semirugosus (Salter MS.). Plate II, figs, lo — 17. 



1878. Bellerojjhori semirugosus, Salter MS., Cat. Camb. Silur. Foss. Mas. Pract. Geol., p. 57. 



Specific Characters. — Shell globose to subglobose ; outer whorl completely 

 enveloping inner whorls, transverse, inflated, with convex sides and dorsum, 

 increasing in size to mouth ; dorsum broad, marked off from sides by narrow 

 revolving raised line, against which thick, low, rounded, equidistant and equal 

 transverse rugse or ribs on the sides of the Avhorl end rather abruptly. 

 Umbilicus closed, rather deep, subcentral. Surface of shell covered with fine, 

 closely-placed, small thread-like granulated transverse lines bending back acutely 

 on the dorsum to form a broad, U-shaped sinus, and with minute revolving lines 

 on sides of whorl crossing the transverse ones, so as to cause their granulation 

 and the fine cancellation of the surface. 



Dimensions. — Height, about 25 mm. ; maximum width, about 19 mm. 



Horizon. — Bala Series. 



Localities. — Tyn y twyl, Grweiddeau; Vyrnwy Dam, Llanwddyn. 



Bemarks. — There are only four specimens of this form known to me, three 

 [28039, 28040, and 28041] in the Jermyn Street Museum from Tyn y twyl and 

 one in the Sedgwick Museum from the Vyrnwy Dam. It is an interesting and 

 peculiar species, for the ornamentation is unlike that in any other species of Sinuites 

 with which I am acquainted. The shape and sinuation of the mouth are unfor- 

 tunately unknown, the margins not being preserved, but from the course of the 

 strige on the dorsum it is probable that there was a broad, U-shaped sinus. The 

 size of the Llanwddyn fragment in the Sedgwick Museum indicates that the shell 

 grew to a larger size than is shown by Salter's type specimens. 



11. Sinuites soudleyensis, sp. nov. Plate II, figs. 18, 19; Plate III, figs. 1 — 3. 



1884. Bellerophon bilobatus, Sowerbj, J. D. La ToucLe, Handbook to the Geology of Shropshire, 

 p. 59, pi. V, fig. 99. 



Specific Characters. — Shell globose to subglobose ; outer whorl completely 

 env^eloping inner whorls ; umbilicus subcentral, minute or closed. Outer 

 whorl transverse, broad, low, rounded, slowly increasing in size to mouth ; 

 dorsum broadly convex, sometimes rather flattened. Mouth slightly expanded at 

 base ; dorsal sinus shallow, open, rounded, broadly U-shaped ; apertural lobes 

 short, rounded, simply arched, not subangular. Shell composed of thin smooth 

 outer layer and thicker second layer ornamented with closely-placed regular 

 transverse rounded lines concentric with margin of mouth, crossed by very delicate 

 revolving lines, most distinct near umbilicus ; on the dorsum the transverse lines 

 become finer, more closely placed, and bend back rather suddenly to form a 

 U-shaped curve less open than dorsal marginal sinus. Occasionally a few low, 



