1835.] Deposit of Recent Marine Shells. 135 



long as the aperture. It is turned to the left, and is a little 

 reflexed. 



The shells which have been found in the Dalmuir sand 

 have in general lost all colour, and become of a dull yellowish 

 white, but otherwise, though brittle, they are in a state of 

 beautiful preservation. They appear to be all natives of 

 the British seas, with the exception of the F. lamellosus, 

 which has only been observed about the Straits of Magellan, 

 and Natica glaucinoides, which is a crag fossil. But the 

 relative proportions in which they occur by no means agree 

 with that in which our seas produce them. On the contrary, 

 in general those which are most common in the sea, appear 

 to be rarest there, while those which are found at Dalmuir 

 in the greatest profusion are mostly rare in the sea. For 

 example, of the Mya truncata, which is one of the commonest 

 shells in the Firth of Clyde, only one imperfect specimen 

 has been found at this place, while Fusus Bammus, Lacuna 

 vincta, Fissurella Noachina, and Astarte minima, none of 

 which are common shells, together with Natica glaucinoides, 

 which is a crag fossil, are very common at Dalmuir. Car- 

 dium edule is extremely scarce, and Mytilus edulis is equally 

 so, and Ostrea edulis has never been met with, while on the 

 other hand, Pecten islandicus, and Patella parva, are very 

 common. From these facts it is evident that the deposit 

 cannot have taken place while the inhabitants of the Firth of 

 Clyde were in every way the same as they are at present. 



The shells which have been assembled in this confined 

 spot, and buried in sand in this extraordinary manner, 

 appear to have been collected from very different situations. 

 The Nucula minuta, and the Velutina, inhabit deep water ; 

 the Buccina, and the Astarte, frequent the sands about low 

 water, in which the Mya truncata and the Cardium edule 

 bury themselves; while the Mytilus and the Modiola attach 

 themselves to rocks in deep water, and the Littorina (and 

 probably the Natica) frequent those rocks which are alter- 

 nately covered and laid bare by the ebbing and flowing of 

 the tide. 



It is remarkable, and is a circumstance which adds to 

 the extraordinary nature of this deposit, that the sand in 

 the immediate neighbourhood of the fossils is quite desti- 

 tute of any traces of shells. Few of the shells which it 



