306 Halph Tate — Oldest Knoicn Trigonia. 



close one to another that one might in vain seek between them room 

 for one's foot, much less for a sleeping-sack. We had always a 

 system of ice-pipes of this kind as substratum when we rested for 

 the night, and it often happened, in the morning, that the warmth 

 of our bodies had melted so much of the ice, that the sleeping sack 

 touched the water, wherewith the holes were always nearly full. 

 But, as a compensation, wherever we rested, we had only to stretch 

 out our hands to obtain the very finest water to drink. 



{To be continued in our next.) 



II. — Note on the Discovery of the Oldest Known Trigonia 



{T. LiNGONENSIS, DuMOKTIER) IN BRITAIN. 

 By Ralph Tate, Assoc. Lin. Soc, F.G.S. 



THE ironstone of Cleveland is a repository for a number of interest- 

 ing species of MoUusca, amongst which a Trigonia deserves 

 especial notice, representing as it does the oldest form of the genus, 

 and now recorded for the first time as British. 



Till within the last few years Trigonia littorata was the precursor 

 of one of the most important generic forms of Mesozoio life, but the 

 publication by Dumortier (Etudes Jurassiques du Ehone, p. 275, 

 1869), of the occurrence of a K%OTO'a (T. Lingonensis) in the Marl- 

 stone of the Ehone Basin robbed T. littorata of its ancient renown. 



T. littorata, Phillips, is stated by its describer (Geol. Yorksh. 1. 14, 

 f. 11) to be from the Lower Lias Shale, Eobin Hood's Bay, and else- 

 where in the same work to be from the Alum Shale. The former 

 statement is doubtlessly a clerical error. It is chiefly to be found in 

 the cement stones above the Alum Shale, but it also occurs in the 

 underlying Shale. This position is on an average 200 feet above the 

 ironstone whence T. Lingonensis was obtained. 



The characters of the fossil are fully displayed, and do not permit 

 a doubt of its generic position ; agreeing, moreover, in size and 

 ornamentation, with the type of T. Lingonensis from the Basin of 

 the Ehone, it must be quoted under that name. 



T. Lingonensis belongs to the Section Glahroe. as defined by 

 Agassiz, which contains a few Portlandian and Cretaceous species. 

 It is noteworthy that the oldest species of the genus represents the 

 simplest type of ornamentation. 



The specimen on which these remarks are based is, however, not 

 the only one of this species in Britain. My friend, Eev. J. F. Blake, 

 informs me by letter April 18, 1872, that a specimen of Trigonia 

 Lingonensis — " in fine preservation, better, as far as I remember, even 

 than yours, — is in the York Museum, labelled ' New Trigonia, by 

 Charlesworth, in 1858.' It is from the ironstone, with green grains, 

 at Maroke" (probably from the Upleatham Mines). 



Position and Localities. Zone of Ammonites spinatus. Loft- 

 house (?) and Upleatham Mines (York. Mus.). 



