ANIMALS. s2'3 
shell, and somewhat prominent. pire conical, but rather flattened at the apex. 
Whorls tumid, rapidly increasing in size, and distinctly separated from each other. 
Aperture orbicular; with the inner lip slightly overspreading a narrow canaliculate 
umbilicus. 
My largest specimen of this pretty species measures nearly half an inch in width, 
and the same in height. It differs in the form of its aperture from the last species, 
which is also more elongated, and much smaller. 
Natica Leibnitziana is a rare species in Shell-limestone at Tunstall Hill, and Silks- 
worth. Dr. Geinitz states that Herr Mielecki has discovered it in Zechstein-dolomite 
in the neighbourhood of Osterode; and at Scharzfeld, and Sachswerfen, in the Hartz. 
Family PLEUROTOMARIID&, King. 
The present group is proposed for the genera Pleurotomaria, Trochotoma, Murchi- 
sonia, and Schizostoma, which are furnished with a fissure in the outer lip, or a row 
of small apertures in the body-whorl, for the purpose of carrying off the vitiated 
currents from the branchial chamber. 
It has existed nearly throughout all organic time, being found in certain of the 
Silurian rocks, and still an inhabitant of the present seas. The next genus is the 
only one known to occur in the Permian deposits of Britain. 
= Genus Pleurotomaria, De France. 
(?) ANatomus,” De Montfort, 1810. 
ScIssuRELLA, A. d Orbigny, 1823. 
Diagnosis.—“ Shell spiral, turbinated, sometimes quite conical, and having either 
a nearly square or somewhat rounded aperture, generally, however, of a sub-quadrate 
form; the outer lip bemg sharp-edged; and having near its upper edge a deep notch 
or fissure near the suture.” 
= 
The genus Pleurotomaria was simply indicated by M. de France, in vol. xh of the 
‘Dictionnaire des Sciences Naturelles,’ in which it is divided into two sections,—the 
umbilicated and non-umbilicated. The first section is typified with Plewrotomaria 
tuberculosa, and the second with Pleurotomaria elongata. These and some other sections 
' Vide King, Catalogue, p. 13. 
? It is much to be regretted, that nothing more seems to be known of this singular genus than what is 
published of it by Montfort. (Vide ‘Conchyliologie Systématique,’ t. 11, pp. 279, 280.) If Iam correct in the 
view herein taken of the habit of Pleurotomaria (vide p. 215), Anatomus cannot be a synonymous genus ; since 
Montfort states, that he saw ‘a large number attached to the stems and leayes of a floating sea-weed (a 
species of Sargassum) by a corneous thread (“une espéce de muscle, en partie corné’’), which passed out of 
the notch in the lip of the aperture. Anatomus appears like a minute Schizostoma. 
3 Sowerby’s Genera. 
