110 



of structure or beauty, being rough and irregularly 

 formed, the substance lamellar and foliaceous; they 

 are attached by a byssus passing through an open- 

 ing at the posterior side of the apices, and at the base 

 of the shell is an open channel formed by the parti- 

 tions of the valves ; the ligament is nearly external, in- 

 serted between the slope of the hinge; the principal 

 cavity of the interior surface is somewhat pearly. Shell 

 linear, oblong, valves flexuous, distorted, and with long 

 transverse lobes on either side of the apices. The white 

 variety is the most rare and valuable; the common 

 sort M. vulgaris is black. 



Malleus albus Malleus vulsellatus 



vulgaris anatinus 



normalis • decurtatus. 



jjjr 



AVICLLA. 



mytilus HiRUNDO. — Linn. 



Sowerbys Genera, No. 1 4, plate 3. 



Lamarck has separated this from the G. Mytilus of 

 Linnaeus. The form of the shell is scarcely less re- 

 markable than that of the Malleus, although of quite a 

 distinct character. The principal part of the shell con- 



