MOLLUSCA. 73 



Mya truncata, L. Op. cit. iii. p. 66, v. pi. 50. f. 2. 



bundani 

 after storms 



Abundant off the mouth of the P]den, and on the beach 



Fam. 21. Saxicavidae, Swainson. 



Genus 2. Saxicava, Fleurian de Bellevue. 



Saxicava rugosa, L. Op. cit. iii. p. 81, v. pi. 51. f. 3 & 4. 



Common at low-water mark amongst the rocks in crevices 

 and holes in sandstone and shale, as well as inside empty 

 limpet-shells and Balani. Often firmly adherent to its cayity 

 by a byssus. 



Fam. 23. Pholadidae, Gray. 

 Genus 1. Pholas, Lister. 

 Pholas Candida, L. Op. cit. iii. p. 107, v. pi. 52. f. 2. 

 Rarely found in shale at the Castle Rocks ; commonly met 

 with on the beach after storms, sometimes in a perfect con- 

 dition. 



Pholas crispata, L. Op. cit. iii. p. 112, v. pi. 53. f. 1. 



Abundant in the soft shale and sandstone at East and West 

 Rocks, and especially opposite the castle. Occasionally the 

 siphons are observed protruding through sand which coats 

 some of the ledges. Young specimens are often cast ashore 

 on the West Sands in water-logged and decayed wood, whence 

 they are extracted by the sea-fowl. 



Genus 3. Xylophaga, Turton. 



Xyhphaga dorsalis, Turton. Op. cit. iii. p. 120, 

 v. pi. 53. f. 4. 



Not common ; several living specimens occurred in the 

 wood of a submerged thorn tree. 



