16 ORDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



14. Sinuites? separatus, sp. nov. Plate III, fig. 12. 



Specific Characters. — Shell subdiscoidal, somewhat compressed, high, witli 

 rather flattened sides and narrowed, flattened dorsum, nearly involute, the outer 

 whorl almost entirely enveloping the others, thickest at umbilicus. Outer whorl 

 higher than wide, rliomboidal in transverse section, narrowing dorsally, slowly 

 increasing in height, with sides somewhat flattened, and having a shallow 

 revolving groove immediately below the edge of the flattened dorsum. Umbilicus 

 minute, deep, situated below middle of shell. Apevtural edge and surface 

 unknown. 



Dimensions. — Height of shell, 21'0mm. ; height of outer whorl above umbilicus, 

 13*0 mm.; thickness of shell at base of mouth, about lO'O mm.; thickness of outer 

 whorl at dorsum, about 4*0 mm. 



Horizon. — Lower Ordovician : Balclatchie Group [conglomerate]. 



Locality. — Balclatchie, Girvan. 



Bemarl's. — Only one specimen of this shell is known to me, and it is in Mrs. 

 Gray's Collection. The true generic position is rather doubtful, and in cross- 

 section the outer wiiorl with its lateral revolving groove suggests Bucaniella; but 

 a somewhat similar groove is seen in some specimens of Sinuites sowerhyi, 

 Perner (non B. Sowerhyi, D'Orb.) and in Temnodiscus platynotus, Perner,^ the 

 resemblance to the latter species being somewhat close, but the umbilicus in our 

 form is much smaller and placed higher, and the outer whorl increases more 

 slowly in height. 



15. Sinuites sphaeroidalis, sp. nov. Plate III, figs. 13, 14. 



Specific Characters. — Shell globose ; whorls transverse, more than twice as 

 wide as high ; outer whorl completely enveloping inner ones and rather rapidly 

 increasing in size to mouth ; umbilicus closed, deep. Dorsum of outer whorl 

 convex. Surface of shell ornamented with fine, sinuous, granulated transverse 

 lines, interlacing and forming a fine reticulation. Mouth Avitli simple rounded 

 apertural lobes and open V-shaped dorsal sinus. 



Dimensions. — Height, about 8 mm. ; thickness at umbilicus, about 6 mm. ; 

 width at mouth, about 7*5 mm. 



Horizon. — Lower Ordovician : Balclatchie Group [conglomerate]. 



Locality. — Balclatchie, Girvan. 



Bemar/iS. — None of the specimens, including the type in Mrs. Gray's Collection, 

 are well preserved, most of them being imperfect internal casts. The margins of 

 the mouth are not well preserved, but the ornament shows up clearly in some parts. 

 Perhaps the American S. granistriata (Ulrich)^ is allied to this Girvan species. 



1 Perner, op. cit., p. 70, text-fig. 51 a — c. 



