ANIMALS. 213 



shell, and somewhat prominent. Spire conical, but rather flattened at the apex. 

 Wliorls tumid, rapidly increasing in size, and distinctly separated from each other. 

 Aperture orbicular ; with the inner lip slightly overspreading a narrow canaliculate 

 umbihcus. 



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 Leihiitziana 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. 



Fmiily Pleurotomariid^,^ King. 



The present group is proposed for the genera Pleiirotomaria, 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 Pleurotoviaria , De France. 



(?) Anatomus,2 De Montfort, 1810. 

 ScissuRELLA, A. d Orhigny, 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 being 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. xli 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 Pleurotomaria 

 tuberculosa, and the second with Pleurotomaria elongata. These and some other sections 



1 Vide King, Catalogue, p. 13. 



2 It is mncli to be regretted, that nothing more seems to be known of this singular genus than what is 

 published of it by Montfort. (Vide ' Conchyliologie Systematique,' t. ii, pp. 279, 280.) If I am correct in the 

 view herein taken of the habit of PZewro^omana (videp. 215), vi??a^o;HMS cannot be a synonymous genus ; since 

 Montfort states, that he saw a large number attached to the stems and leaves of a floating sea-weed (a 

 species of Sargassum) by a corneous thread ("une espfece de muscle, en partie corne"), which passed out of 

 the notch in the hp of the aperture. Anatomus appears like a minute Schizostoma. 



3 Sowerby's Genera. 



