ANIMALS. 217 
Dagnosis.—‘‘ 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 striz, 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 Vernewil. Howse, Trans. T. N. F. C., vol. i, p. 238, 1848. 
Diagnosis.—Umbilicated : twice as wide as it is high. Spire depressed. Whorls 
evenly rounded: marked with rather prominent spiral lines. 
This species differs from both Plewrotomaria antrina, and P. Tunstallensis, in having 
the spire decidedly more depressed; and from M. de Verneuil’s Plewrotomaria penea, 
im 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&, Sander Rang. 
Genus Dentalium, Linneeus, 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. 
? Monograph of the Crag Mollusca, p. 187. 
CC 
