216 PERMIAN FOSSILS. 



unusually produced, and the upper half of the whorls flattened, as exampled in the 

 specimen represented by fig. 6, PI. XVII ; in these respects it agrees very closely 

 with Dr. Geinitz's Pleurotomaria Verneuili : the specimen of the latter represented in the 

 ' Versteinerungen,' pi. iii, fig. \8 a, d, c, however, appears to have a wider umbilicus. 

 My largest specimen is five eighths of an inch in height axially. 



Pleurotomaria antrina is rather common in some places; for example, Tunstall Hill, and 

 Silksworth, in Shell-limestone ; but somewhat rare at Humbleton Quarry, Castle Eden- 

 Dene, and Dalton-le-Dale, in the same rock ; and extremely rare at Tynemouth-Castle 

 Cliff in the Breccia. According to Dr. Geinitz, it occurs in the Zechstein-dolomite at 

 Gliicksbrunn and Konitz ; and according to Credner, near Asbach and Schmalkalden. 



Pleurotomaria Tunstallensis, Kini;. Plate XVII, figs. 3, 4, 5. 

 Pleurotomaeia Tunstallensis, ^««^. Catalogue, p. 14, 1848. 



Diagnosis. — Conical. Whorls evenly rounded ; marked with fine spiral lines, and 

 slight incremental striae. Aperture sub-orbicular : with the pillar-lip oblique. Fissure 

 deep, and situated in the medio-longitudinal part of the whorls. 



This species resembles the last in form ; but it is non-umbilicated, and its pillar-lip 

 is oblique : it is also related to Pleurotomaria striata, J. Sow. ; but instead of the 

 umbilicus being closed by a somewhat thick and a rather broad callosity, which is the 

 case with the lattier, according to De Koninck, it is without any callosity, and its 

 pillar-lip is sharp, though a little reflexed. The apical whorls are occasionally trans- 

 versely plicated near the suture ; as displayed in the enlarged representation at fig. 5, 

 PI. XVII. 



Although this and the preceding shell have been specifically separatfed, I have 

 considerable doubts as to their really being distinct, — or, perhaps, it would be better 

 to say, that I feel considerable difficulty in separating them : whether this is owing to 

 there being no specific difference between them, or to their closely simulating each 

 other, I am certainly not much disposed to contend for : if, however, it be necessary 

 to unite them, it will almost be impossible, from their various modifications, to draw 

 up any other than a very general diagnosis of the species. My largest specimen 

 measures a quarter of an inch in its axial length. 



Pleurotomaria Tunstallensis occurs at Tunstall Hill in Shell-limestone ; but not so 

 often as the last species. 



Pleurotomaria nodulosa, Ki7iff. Plate XVII, fig. 9. 



Pleukotomaria nobulosa, King. De Verneuil, Bull. Soc. G^ol. de France, 2"'*serie, 



vol. i, p. 35, 1844. 



— — „ Geol. Russ., vol. i, p. 225, 1845. 



— — „ Tennant, Strat, List, p. 89, 1847. 



— — „ King, Catalogue, p. 14, 1848. 



— — „ Howse, Trans. T. N. F. C, vol. i, p. 238, 1848. 



