250 NOTE 8 ON THE PERMIAN SYSTEM OE 



This species was first described under the above name in the 

 " Trans. Tyneside Nat. Fiekl Club,'' where also some other pecu- 

 liarities are pointed out by which it may be known and distin- 

 guished from the preceding species. The testimony of Voir 

 Buch in favour of this opinion is singular, for at the same time 

 that he separates Terehnitula Sddotlmmi from the T. lacunosa, 

 with which it had been confounded by early authors, he expressly 

 says that the latter is found in the magnesian limestone at 

 Humbleton. It is admitted doubtfully into the list of Permian 

 Fossils in the " Geol. Russ." vol. 1, under the latter name, 

 but none of the specimens from Ilmenau which I have seen are 

 referable to this species. 



It occurs in the shell-limestone at Humbleton, sometimes in 

 considerable abundance. I have never found it at Dalton, nor 

 do I think that it occurs tht-re. I have, however, taken one 

 specimen from the magnesian-conglomerate of Tynemouth. It 

 is a very local species, and has not yet been found, 1 think, in any 

 foreign locality. 



8. SPIRIGERA, ^r(9/'%;^y. 



1. S. PECTINIFERA, SoiV. 



The internal structure of this very interesting shell is not 

 correctly represented in King's " Monograph," so far as I am 

 able to judge from specimens collected at Humbleton. In the 

 enlarged figure, tab. 10, fig. 9, the platform, or expansion be- 

 tween the crura of the loop, is much too large, and in fig. 10 the 

 coil is represented with small blunt pectinations round its outer 

 margin. This serrated appearance is due to mineralization, for 

 upon close examination the entire coil of some examples is found 

 to be covered all over with fine crystals. In the greater number 

 of specimens of the interior that I have seen, the coil aj)peared 

 quite smooth. For the perfect understanding of this species it 

 will be necessary to consult Mr. Davidson's excellent plates, 

 Mon. Brit. Perm. Brach. pi. 1, figs. 50-5G ; pi. 2, figs. 1-5, in 

 which all the peculiarities of this singular shell are carefully 

 represented. I have not, however, up to Iho present time, been 



