64 ORDOVICIAN AND SILURIAN BELLEROPHOXTACEA. 



and meeting ai (30° — 70°, Slit-band narroAV, slightly elevated on carina. Umbilicus 



o 



completely closed, subcentral, with callosities projecting laterally and supporting 

 expanded basal angles of mouth. Mouth triangular, widest at base, with shallow 

 broad open V-shaped sinus in upper lip and infolded (?) lateral lips. Surface of 

 shell ornamented by strong widely-spaced equidistant lamellose lines arched 

 back gently but bending back suddenly close to slit-band to meet it at 

 about 30°. 



Dimensions. — Height c. 30 mm. ; thickness at base of mouth c. 35 mm. 



Horizon. — Bala Beds. 



Locality. — Desertcreat, Tyrone. 



Remarks. — The want of symmetry noticed by Portlock may be due to the 

 distortion of the specimen, or it may be natural, for Cymbularia is frequently 

 asymmetrical, as Perner has noticed and as Lindstrom 1 has mentioned to be the 

 case in his Belter ophon [Cymbularia] fastigiatus. The species is imperfectly known, 

 and there are only three crushed examples for examination. The type-specimen 

 [27998] and the paratypes [27999 and 28000] are ail in the Jermyn Street 

 Museum. 



The original description is meagre and runs as follows : " Back sharply 

 angular; aperture expanded, with flattened wing-like sides, triangular from the 

 angularity of the back, and without a sinus ; spire suddenly involute, not umbili- 

 cated. The striae proceeding from the wings to the back are curved, and the wings 

 have also a twisted appearance and are not quite symmetrical." 



The relations of this species to ('. drummuchensis from the Druinmuck Beds 

 (Up. Bala) of Girvan (see below) are close, but the ornamentation of the surface is 

 different. 



2. Cymbularia carinata (Sowerby). Plate X, fig. 12. 



1839. Belierophon carinatus, Sowerby, in Murchison's Silurian System, p. 604, pi. iii, fig-. -1. ami 1 d. 



? 1839. Belierophon carinatus, Sowerby, ibid., p. 613. 



1848. Belierophon carinatus, Sowerby, Fi'russac & D'Orbigny, Hist. Nat. Cephal., vol. i. p. 209, pi. ix, 



fig. 12. 

 1852. Belierophon carinatus, Sowerby, McCoy (pars), Syn. Brit. Pal. Foss. Woodw. Mus., fasc. ii, 



p. 309. 



Specific Characters. — Shell sublenticular, of few whorls, somewhat compressed. 

 Umbilicus open, rather deep, with a diameter of less than one-third the height of 

 the shell, with subrectangular umbilical edge and very short steep umbilical slope. 

 Whorls subtriangular, but rounded in cross-section ; inner whorls partly exposed 

 in umbilicus ; outer whorl rather rapidly expanding in height and width, with 

 gently convex sides and subangular dorsum bearing carina. Mouth transversely 



1 Lindstrom, op. cit. p. 77. 



