LAND AND FRESHWATER MOLLUSCA OF SCOTLAND 235 



another specimen of a Rhizodont fish from Dura Den, 

 showing the hinder part of the body and tail ; the caudal fin 

 being well preserved and rhombic-diphycercal in its contour, 

 which is thus conformed as it is in the Lower Old Red 

 Sandstone genus Gyroptychius of M'Coy. There seems 

 every reason for believing that this specimen is both 

 generically and specifically identical with the one described 

 above, as showing the head without the tail, though it may 

 be doubted if the form of the tail alone is sufficient, consider- 

 ing the bad condition of the scales, to justify the reference of 

 the species to the genus Gyroptychius. For the scales of 

 Gyroptychius have a peculiar long ridge on the under surface 

 which cannot be seen in the specimens under consideration. 



The reference of this Dura Den Rhizodont to a genus 

 can therefore meanwhile only be provisional, but as it closely 

 resembles Gyroptychius, so far as its state of preservation 

 allows us to judge, I propose to include it in that genus 

 under the name of Gyroptychius Heddlci. 



I have, in conclusion, to thank the Committee of the St. 

 Andrews Museum for facilities kindly allowed me for 

 examining and describing the fossil. 



ADDITIONS TO THE AUTHENTICATED COMITAL 

 CENSUS OF THE LAND AND FRESHWATER 

 MOLLUSCA OF SCOTLAND. 



WM. DENISON ROEBUCK, F.L.S., 



Hon. Sec. and Recorder to the Conchological Society of Great Britain 



and Ireland. 



I HAVE some further notes to submit in continuation of my 

 paper in the " Annals of Scottish Natural History " for April 

 1892, pp. 104-107, mostly the result of the work of my 

 friends Mr. William Evans, F.R.S.E., and Rev. George 

 Gordon, LL.D. 



6. Helix rufescens on Stirling Castle Rock. This is an addi- 

 tion to the Stirlingshire list, and an important extension to the 

 north-east of the Scottish range of the species. Mr. Evans collected 



