Correspondence — Mr. R. B. Newton — Mr. W. Card. 525' 



ON THE GENUS TREMATONOTUS. 



SiK, — During the preparation of my paper on Trematonotus, pub- 

 lished in the Geological Magazine for August, I much regret 

 having overlooked a valuable monograph by Professor Lindstrom, 

 " On the Silurian Gastropoda and Pteropoda of Gotland" (K. Svensha 

 Vet.-Akad. Hancll. 1884), containing descriptions and figures of two 

 new species of this genus, viz. : T. longitudinalis and T. compressus. 



The former of these shells, to which my remarks will now apply, 

 was stated by its author to resemble so closely Bellerophon dilatatus 

 of James de Carle Sowerby that he would have identified it as such, 

 but for the absence of any mention of dorsal perforations either in 

 the original description or in McCoy's later account of the same 

 species (Pal. Foss. 1852, p. 309). 



It was reserved for the Reviewer of Professor Lindstrom's work 

 (Dr. G. J. Hinde) to point out that " T. longitudinalis is identical 

 with Bellerophon dilatatus ; as the type specimen of this form shows 

 distinct traces of the characteristic apertures on the dorsal keel " 

 (Geol. Mag. 1885, p. 39). 



An examination of the Sowerby type did not convince me that 

 this evidence was complete ; but Dr. Hinde has recently shown me 

 another specimen of B. dilatatus in a better state of preservation, 

 belonging to the Jermyn Street Museum (No. vii. sV) which pos- 

 sesses unmistakably the elongate perforations, so that all doubts, in 

 my mind, are now removed as to the true nature of this classical 

 species. 



With regard to my T. Britanniciis, although more ovate in contour 

 and very deficient in its umbilical characters, through pressure, yet 

 its ornamentation and perforations are so like the Swedish specimen 

 that they may be looked upon as practically the same species. The 

 effect of this will be that T. Britannicus, like T. longitudinalis, will 

 fall into synonomy under the older name of T. dilatatus. 



In conclusion, I wish to record my indebtedness to Dr. Hinde for 

 assisting me in this determination, and to assure Prof. Lindstrom 

 how sorry I am that his monograph escaped my attention. 



Nat. Hist. Museum, E. Bullen Newton. 



October 12th, 1892. 



ON THE FLEXIBILITY OF EOCKS. 

 SiE, — ^With regard to the localities in Durham at which Flexible 

 Limestone occurs. I find that Prof. G. A. Lebour refers to several 

 in his " Outlines of the Geology of Northumberland and Durham." 

 At the time of writing the description of this rock published in the 

 March Number of the Geol. Mag. (1892), I had no opportunity of 

 referring to this work. Prof. Lebour kindly informs me that the 

 variety from Marsden loses its flexibility after being kept in a dry 

 place for some time. My specimens from Sunderland do not appear 

 to have undergone any loss of flexibility as yet. 



Eoyal College op Science, George W. Card, A.R.S.M. 



October 3rd, 1892. 



