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



growth up to the adult state, he would have deserved our best 

 thanks, and would have contributed something towards the full 

 understanding of its true character. But it has pleased him 

 better, instead of so doing, to represent and describe the young 

 of it as a new species, — N. Bower bankianus. The last chamber 

 only is the part principally represented of N.Frieslebeni, and from 

 it the characters of the whole shell, with the aid of Geinitz^s 

 description, appear to be drawn; for the figure, pi. 17. fig. 16, 

 does not contribute much towards the elucidation of the species. 



If one examines the principal characters of Mr. King^s new 

 species, viz. "deeply umbilicated; whorls increasing rather ra- 

 pidly in size ; slightly embracing (?) each other, '^ it will be seen 

 that they are only the characteristics of young individuals ; if 

 they are anything more, it will be necessary, in order to esta- 

 blish the specific identity of N, Bowerbankianus, for Mr. King 

 to represent the young state and mode of growth of N. Friesle- 

 beni, and show in what points they differ. Until this has been 

 done, it is better to consider N. Bowerbankianus as the young 

 state of the present species. 



Very young specimens are much rounded in form, and orna- 

 mented with strong, decussated striae. The outer chamber of 

 Mr. Kirkby^s largest specimen is nearly 4 inches in length, and 

 2\ in greatest breadth. 



In the shell-limestone of Tunstall, Humbleton, Dalton-le- 

 dale, &c., and, according to Mr. King, in the compact limestone 

 of Whitley. 



Pteropoda. 



43. Theca? Kirkbyi, n. s. PL IV. fig. 27, restored. 



Shell straight y tapering gradually ; aperture transversely oval ; 

 surface with small, transverse, wavy furrows : four thin decurrent 

 wings run along the whole length of the shell. 



This is the only Pteropod that I am acquainted with in the 

 English Permians. The restored outline in the accompanying 

 plate will serve to give an idea of its form and size. I have 

 found only one specimen which shows the above characters, and 

 which indicates probably a closer alliance with the Creseis, Rang, 

 than with the genus in which it is provisionally placed. 



It is dedicated, with great respect, to Mr. James Kirkby of 

 Sunderland. 



From the shell-limestone of Tunstall. 



It seems desirable to substitute the term " BotryoidaP^ for 

 the epithet Conglobated, proposed in a former part of this paper ; 



