Counties of Durham and Northumberland. 471 



surface is ornamented with distinct longitudinal lines, but they 

 are never so much raised as in the following species, and the 

 surface never pi'esents the same finely decussated appearance. In 

 young specimens the suture follows the line of the fissure of the 

 preceding whorl, but it falls considerably below it in some adults, 

 which have consequently a less conical appearance. The upper 

 surface of the whorls is either slightly arched or nearly flat- 

 tened, and this variation is respectively represented on the under 

 surface, which has, in the latter case, a flattened, truncated, and 

 in the former a tumid appearance. These variations are shown 

 in the figures referred to in the accompanying plate. 



The false species and erroneous identifications of this very 

 characteristic shell are corrected in the Table given at p. 39 ; 

 but the last two synonyms must be cancelled, for reasons stated 

 under the preceding and under the following species. 



Rather plentiful in the shell-limestone of Tunstall, but rare 

 in several other localities. 



41. Pleukotomaria Verneuili, Geinitz. — I find, since the 

 Table of species was printed, that Baron Schauroth has identified 

 the Pleurotomaria nodulosa, King, with the Pleurotomaria Ver- 

 neuili, Geinitz. As this identification is undoubtedly correct, 

 and as Geinitz's description and figure appeared several months 

 before King's Catalogue, the name adopted above has right of 

 priority. 



In well-preserved specimens the whole surface of the shell is 

 ornamented with strong, longitudinal, raised lines, which being 

 cut obliquely by the strong lines of growth, give the whole sui*- 

 face a beautifully decussated appearance. The double row of 

 nodules is not so persistent a character as the former, for the 

 sutural row is not seen on young individuals, and the row placed 

 below the fissure becomes obsolete in very large full-grown spe- 

 cimens. It appears to have been the most beautiful and deli- 

 cate shell of the Permian seas, and from the numerous examples 

 of bored shells that occur, — a fact which I first pointed out to 

 Mr. King, — it probably, with its congener P. antrina, preyed 

 upon its more peaceful and unprotected neighbours. 



The specimen figured in 'Perm. Mon.^ is a young individual. 

 The largest specimen I have seen exceeded an inch in length and 

 width. 



It occurs in the shell-limestone of Tunstall and Humbleton. 



Cephalopoda. 



42. Nautilus Prieslebeni, Geinitz. PI. IV. fig. 26,juv. 

 If, instead of dismembering this fine species, Mr. King had 



endeavoured to trace its variations through all its periods of 



