CHAP. XXII.] MOLLUSCA. 511 



Family 16.— HALIOTID^. (G Genera, 106 Species), 



DiSTKiBUTiON. — The Ear-shells are most abundant in the 

 Indian and Pacific Oceans ; some are found on the east coasts 

 of the Atlantic, but there are very few in the West Indies. 

 lanthina (10 sp.) consists of floating oceanic snails found in the 

 warm parts of the Atlantic. Three other genera are fossil, and 

 there are near 500 fossil species of this family ranging from the 

 Lower Silurian to the Pliocene formations. 



Family 17.— FlSSUKELLIDiE. (5 Genera, 200 Species). 



DiSTEiBUTiON. — All seas. Pundurella (6 sp.) is confined to 

 Northern and Antarctic seas ; Rimula to the Philippines ; and 

 Parmophorus (15 sp.) from the Cape of Good Hope to the 

 Philippines and New Zealand. There are about 80 fossil 

 species, ranging from the Carboniferous formation to the 

 deposits of the Glacial epoch. 



Family 18.— CALYPTR^ID^. (4 Genera, 125 Species). 



Distribution. — The Calptrseidse, or Bonnet-Limpets, are 

 found on the coasts of all seas from Norway to Chili and 

 Australia ; but are most abundant within the Tropics. The 

 genera are all widely scattered. There are 75 fossil species, 

 ransing from the Devonian to recent formations. 



Family 19.— PATELLID^. (4 Genera, 254 Species). 



Distribution. — The Patellidse, or Limpets, are universally 

 distributed, and are as abundant in the temperate as in 

 tropical seas. There are about 100 fossil species, ranging from 

 the Silurian to the Tertiary formations. 



