ANIMALS. 217 



Diagnosis. " Spirally threaded, the threads crossed with rather strong lines of 

 growth : with two spiral rows of tubercles, one situated immediately below the sinual 

 band, and the other close to the suture : the sinual band is concave, and furnished 

 with a mesial thread." (King.^) 



This, the prettiest species of the genus belonging to the Permian system, is readily 

 distinguished by its prominent decussated sculpturing, and its two rows of wave-like 

 nodules, one adjoining the suture, and the other below the line of the fissure-band. It 

 is decidedly umbilicated, and has a sharp slightly-reflexed perpendicular pillar-lip. 

 The spiral or longitudinal lines are stronger than the incremental strise, and the lip on 

 each side of the fissure is rounded. My largest specimen measures five eighths of 

 an inch axially. 



Pleurotomaria nodulosa is an exceedingly rare species, having occurred to me but 

 very seldom at Tunstall Hill and Humbleton Quarry, in Shell-limestone. 



Pleurotomaria LiNKiANA, King. Plate XVII, figs. 7, 8. 



Pleurotomaria Permiana, King {partim). Catalogue, p. 13, 1848. 



— PENEA, De Verneuil. Howse, Trans. T. N. F. C, vol. i, p. 238, 1848. 



Diagnosis. — Umbilicated : twice as wide as it is high. Sjjire depressed. Whorls 

 evenly rounded : marked with rather prominent spiral lines. 



This species differs from both Pleurotomaria antrina, and P. Tunstallensis, in having 

 the spire decidedly more depressed ; and from M. de Verneuil's Pleurotomaria penea, 

 in having the whorls evenly rounded, and not medio-longitudinally carinated. The 

 specimen figured is a quarter of an inch wide, and an eighth of an inch high. 



Pleurotomaria Linkiana is a rare species : it has occurred to me only at Humbleton 

 Hill and Dalton-le-Dale, in Shell-limestone. 



Order Cirrhobranchiata, De Blainville. 

 Family Dentaliid.e, Sander Rang. 



Genus Dentalium, Linnaeus, 1740. 



Diagnosis. — " Shell tubular, symmetrical, elongato-conical, or sub-cylindrical, gene- 

 rally smooth ; sometimes annulated, often costated ; slightly curved, open at both ends ; 

 smaller at the posterior extremity, which is sometimes entire, sometimes with a medial 

 and dorsal cleft, occasionally with two lateral indentations." (Searles Wood.^) 



' Catalogue, p. 14. 



2 Monograph of the Crag Mollusca, p. 187. 



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