T. McK. Hughes — Man in the Crag. 



249 



removed, the tooth would be found to be pierced by a clean-cut hole 

 representing the middle portion of the lithodomus chamber. If the 



Fig. 3. Large tooth, of Carcharodon 

 megalodon, Agassiz, from Crag. Out- 

 line restored by dotted line. 

 a h line of section through the hole. 



Fig, 3o. Section through lithodomus cell 

 along the line a 6 of Fig. 3. 



animal bored through the clay and only just touched the tooth, it would 

 be eaten out into one of those basin or saucer-like cavities so com- 

 mon over most of these Crag fossils. Boring gasteropods, burrowing 

 sponges, the wear and decomposition of the fossil along broken or 

 softer and more soluble portions, must also be taken into account. 

 From the nature of the case, therefore, we might expect to find 

 sometimes regular, sometimes irregular cavities, as the hole was 

 driven right through from one side only, or two holes from opposite 

 sides were afterwards united. 



Thus we have evidence that animals which could produce these 

 holes did live in the Crag sea, and the exceptional cases where they 

 bored through, or where the partition between two holes on opposite 

 sides was broken through, can be easily explained. 



