TESTACEA. 47 



and safety — that it seems unaccountable how they should have been thu.« 

 connected. 



Yet as everything is harmonious in nature, and evidently the result 

 of design, we are bound to conclude that some wise purpose contemplated 

 this singular device, and thence suppressing conjectures that nature has 

 erred, either in tlie true proportions or their utility, as our ignorance may 

 have led us to entertain them. 



Our knowledge of the Logarithmic Spiral Testacea is now confined 

 to minute species comj^aratively, of which, if I be not mistaken, the 

 greater proportion may be found in the fresh waters. But fossil remains 

 bear testimony to the existence of very much larger shells, consequently 

 their animals of this peculiar formation, scarcely any of which are known 

 to exist in a living state at the present day. 



Such are the Ammonites, of which numbers are dug from the bowels 

 of the earth in different quarters of the globe. Some of gigantic dimen- 

 sions may have inhabited the primgeval world. 



Those spiral shells yet preserved in miniature are not less curious 

 and interesting. I have seen none but what are occupied by a Uina.r or 

 heli.f. 



Planorbis inconspicua. 



This minute subject, if it could be identified with one which has 

 been already described, is said to be obtained in a fossil state. 



Figure flattened on both sides ; a logarithmic spiral, consisting of 

 three volutions ; diameter under half a line ; animal a Umax ; tentacula 

 two, cylindrical, a conspicuous black eye at the external root of each : 

 operculum round ; colour of the shell amber-brown, of the animal grey. 



Marine ; obtained by washing the fuci growing under low water at 

 Eyemouth. 



Among a number, none were larger ; all mere specks to the naked 

 eye. 



