457 



CALYPTR^ID^. 



This group of Limpets consists of animals which have a 

 patelliform shell, with an expanded and entire month, and 

 an apex which exhibits more or less of a spiral conformation. 

 The interior is either quite open or divided by a variously 

 shaped shelly process. The animal has a distinct head 

 and tentacula, the eyes being placed on the external bases 

 of the latter organs. The muzzle is sometimes lengthened, 

 but there is no true proboscis. The branchial plume is 

 single. The tongue is studded with teeth ranged in rows 

 of seven, that in the centre differently formed from the 

 hook-shaped laterals. This dentition is very different from 

 what is seen in the neighbouring tribes, and seems to 

 indicate affinities with Velutina and other distant genera, 

 which cast some doubts on the true position of the group. 

 The foot has never any cirrhi ornamenting the sides. 



In our seas there are but very few members of this 

 family ; in tropical regions they are numerous and greatly 

 varied. 



PILEOPSIS, Lamarck. 



Shell conical, entire, dilated at the aperture, and having 

 the vertex, which is posteal, slightly recurved ; outer sur- 

 face usually striated, and invested with a corneous epi- 

 dermis : interior with a horse-shoe muscular impression, 



VOL. II. 3 N 



