14 ORDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



transverse, rounded rugse are present near umbilicus, but die out on sides. Third 

 or inner layer of shell smooth. Interior of shell with broad, low, rounded, marginal 

 thickening on edge of dorsal lip, dying out laterally. 



Dwiensions.— Height, 22 mm. ; thickness at umbilicus, 16 mm. 



Horizon. — Bala Series. 



Localities. — Soudley, near Craven Arms ; Hope Bowdler ; Horderley ; 

 Meifod ?. 



Bemarhs. — The presence of three layers to the shell is well seen in some 

 specimens, but the species is usually represented l)y internal casts. It differs 

 from the true ;S'. hilohatus in being more globose, in having rounded apertural 

 lobes to the mouth, and a shallower, more open dorsal sinus. The ornament on 

 the second layer is well seen in a specimen [28026] from Horderley in the Jermyn 

 Street Museum, and this has the outer smooth layer also partly preserved, as 

 well as showing the smooth surface of the innermost layer. This species, which 

 is abundant at Soudley, seems allied to 8. cancellatus (Hall),^ but less so than 

 8. 'pusgillensis. 8. haldatchiensis, above described, has a closely similar apertural 

 curve, but is less globose and differs also in the ornamentation. 



The co-types are in the Sedgwick Museum and in Jermyn Street. 



12. Sinuites subrectangularis, sp. nov. Plate III, figs. 1—11. 



Specific Gltaracters. — Shell subglobose or somcAvhat compressed, higher than 

 wide, with dorsum strongly arched and whorls increasing more rapidly in 

 width than height. Umbilicus closed, situated at rather less than half the height 

 of shell. Outer whorl completely enveloping inner ones, increasing in width to 

 mouth and more slowly in height, with cross-section transverse and dorsum usually 

 becoming broadly rounded towards mouth. Mouth with broad, deep, V-shaped 

 sinus in outer lip and subangular prominent large somewhat flattened apertural 

 lobes, the inner and anterior edges meeting at 75° — 90° ; base of lip somewhat 

 swollen and decurrent at sides. Surface of shell marked with transverse 

 growth-strise and ridges somewhat irregular in strength and strongest near 

 apertural margin. Interior of shell with low rounded transverse thickening, 

 situated a little distance behind base of sinus and only weakly sinuated in middle, 

 forming a shallow, rounded, median lobe and a broad, low lateral saddle on each 

 side, making an acute angle with the growth-striae and continued with somewhat 

 diminished strength down to umbilicus. General surface of interior finely granu- 

 lose, with coarser granulation on the internal thickening. 



Dimensions. (Narrow variety.) 



Height of shell . . . 21 — 28 mm. . 34 mm. 



Width at mouth . . . 25—30 „ . 26 „ 



Horizon. — (1) Upper Ordovician : Dnmimuck Group. (2) Bala Series. 

 1 Ulrich aud Scofield, o^. cit., p. 872, pi. Ixiii, figs. 1— 14. 



