PLEUROTOMARIA. 407 



Relations and Distribution. — Closely related by its concave spire and general 

 character to the two preceding species, PI. Bessina and its numerous varieties 

 represent the most wide-angled forms of the mutabilis-grovp. In this country it 

 is essentially a fossil of the Parkinsoni-zone, and is not uncommon in that horizon 

 at Halfway House. 



342. Pleueotomaria Dundeiensis, Taumey, 1873. Plate XXXIV, fig. 11. 



1873. Pleueotomaeia Dundeiensis, Tawney. Dundry Gasteropoda, p. 46 (38), 



p). iii, fig. 3. 



Description : 



Height . . . . .27 mm. 



Basal diameter . . . .32 mm. 



Spiral angle ..... 75°. 



Shell regularly conical and moderately umbilicated. Whorls (about seven) flat 

 and close together, the anterior ones being- slightly undercut owing to the 

 development of a broad basal ring. The spiral ornamentation is strong 

 throughout, with marked reticulation in the earlier whorls ; the posterior half of 

 the last two whorls is ornamented by thick oblique costae, rather wide apart. 



The sinus-band is submedian, of moderate width and salience, with a raised 

 line in the centre (where this feature happens to be preserved). The body-whorl 

 is relatively large, subangular at the periphery ; the base is somewhat concave 

 midway to the umbilicus, with strong spiral ornament radially decussated. 

 Aperture rhomboidal and depressed, the inner lip very oblique. 



Relations and Distribution. — In this species Tawney fancied that he traced a 

 resemblance to PI. Mysis, d'Orbigny, a Middle Lias fossil not hitherto identified in 

 England. Indirectly PI. Dandriensis is connected with the Fasciata-grou\). 

 Rare at Dundry, and only doubtfully identified elsewhere. Not, perhaps, a very 

 satisfactory species. 



343. Pleueotomaeia distinguenda, Tatvney, 1873. Plate XXXIV, fig. 10, and 



Plate XXXV, fig. 1. 



1873. Pleueotomaeia distinguenda, Tawney. Dundry Gasteropoda, p. 45 (37), 



pi. iii, fig. 2. 

 Description : 



Height . . . . .18 mm. 



Basal diameter . . . .20 mm. 



Spiral angle ..... 70°. 



53 



