470 Mr. R. Howse on the Permian System of the 



men closely resembles the R. obtusa, but its spire is longer, 

 being more perfect than the others at the apex. 



The estuarine character of these Lancashire shells was pointed 

 out, many years ago, by Mr. Binney, in the ' Manchester Geo- 

 logical Transactions,' vol. i., and this opinion was very forcibly 

 impressed upon me when examining the originals belonging 

 to that gentleman. The larger and more typical individuals 

 from the shell -limestone of Durham have probably lived in less- 

 confined habitats, but still they have a decidedly littoral charac- 

 ter. It must be mentioned here, that I have used the term ' lit- 

 toral ' in contradistinction to ^ pelagic,' and not in the limited 

 sense in which it is used by British naturalists. 



This species occurs in the middle and upper divisions of the 

 magnesian limestone, but the most typical and finest specimens 

 are from the shell-limestone of Tunstall. 



39. LiTTORiNA Hercynica, Geinitz. — This species had been 

 described and figured by I)r. Geinitz in the ' Versteinerungen,' 

 several months before Mr. King's imperfect notice of it in the 

 ' Cat. Org. Rem.' appeared. It was identified in the Tyneside 

 Catalogue with Natica minima, Brown ; but an examination of 

 the latter proves this identification to be incorrect. Dr. Geinitz 

 and Mr. King both place this shell in the genus Natica, but it 

 is rather difficult to comprehend why they do so, for it has a 

 nearly orbicular mouth, is not apparently a polished shell, is not 

 umbi Heated, and bears a strong resemblance to the Littorina. 

 By comparing the mouth of this species (Perm. Mon. pi. 16. 

 f. 28) with that of L. helicina (pi. 16. f. 22), it will be seen how 

 strikingly similar to each other they are in form. In Mr. King's 

 figures, the spire of the shell is represented much too high, and 

 his " diagnosis" is so jumbled, that it would be in vain to hope 

 to identify the species by it. 



The surface of the shell is ornamented with very fine, wavy, 

 longitudinal striae. This peculiar character is well displayed on 

 some specimens collected by Mr. Kirkby at Field House. 



Baron Schauroth has lately united this species to the Euom- 

 phalus Permianus, King, at the same time removing the 

 latter into the genus Rissoa. After examining some examples 

 of this supposed species from both German and English locali- 

 ties, I think it is probably only the young of Littorina Hercy- 

 nica. The figure given by Mr. King, with its few whorls and 

 unfinished mouth, is evidently only a young shell. 



In the shell-limestone of Tunstall, Silksworth, and Field 

 House, but not common. 



40. Pleurotomaria antrina, Schloth. PI. IV. figs. 21, 

 22,23,24 25. 



In well-preserved specimens of this shell, the whole of the 



