NATURAL HISTORY SOCIETY OF GLASGOW. 175 



marshes and on the banks of English rivers, being an example of 

 the great elasticity such animals seem to possess in accommodating 

 themselves to different conditions of habitat and temperature. 



Since writing the above notes I have learned that Planorhis 

 complanatus has been before recorded as occurring in Scotland 

 by Mr William Haddin in his paper on the Distribution of the 

 Helicidae* but what adds to the interest is that his specimens, 

 which he names P. marginatus, were also taken in Lochend Loch, 

 which appears still, so far as known, to be its only Scottish 

 habitat. 



III. — Notes on an adherent form of Productus. 

 By Mr John Young, F.G.S. 



Mr Young remarked that the recent discovery by Mr James 

 Bennie, of the Geological Survey of Scotland, of a small adherent 

 form of Productus was a point of considerable interest, when taken 

 in connection with what are supposed to have been the uses of 

 the long tubular spines which are fixed chiefly upon the auricular 

 expansions of the ventral valves of many species of Produdi. 

 Various opinions have been given as to the uses of these spines, 

 but that entertained by some Palaeontologists is, that they were 

 used to moor the shells in the mud in which they lived, some 

 species, such as Productus semireticulatus, having the spines as 

 long as from four to six inches. In the interesting little form of 

 Productus discovered by Mr Bennie, and which has been figured 

 and described by Mr Robert Etheridge, jun., F.G.S., in the 

 " Quarterly Journal of the Geological Society of London," Vol. 

 xxxii., p. 454, under the provisional name of Productus complectenSy 

 we have the interesting fact revealed, that here there is a small 

 form of Productus in which the tubular spines are adherent to 

 foreign bodies, such as the small stems of crinoids, which they 

 have often circled or embraced while the crinoid was yet in the 

 living state, the crinoid in some instances having afterwards 

 completely enfolded the Productus. Specimens of this Productus^ 

 in various stages of envelopment by the crinoid, are figured by 

 Mr Etheridge, the complete enfolding being indicated by a 

 swelling on the stem of the crinoid. It has been conjectured 



* Proc. Nat. Hist. Soc. Glas., Vol. I., p. 247. 



