MADEIRA AND THE CANARIES 



297 



as a whole, is closely related to the Tertiary fauna of southern 

 Europe. 



Twenty-six species of univalve MoUusca, the majority being 

 modified forms of Hydrohia^ have been described from the Caspian, 

 m.n\Q\j ^ Mlcromelania (6), Caspia (7), Olessinia (^~)^ Nematurella 

 (2>)^Litlioglyphus (V) ^ Piano rh is (l},Zagrahica (V)^IIydrohia (2), 

 Neritina (2). The bivalves are mostly modified forms of Cardium 

 (^Didacna, Adacna^ Mo7iodacna)^ which also occur in estuaries 

 along the north of the Black Sea. A form of Cardium edule 

 itself occurs, and numberless varieties of the same species are 

 found in a semi-fossil condition in the dry or half dry lake-beds, 

 which are so abundant throughout the Aral district. 



((i) The Atlantidean province consists of the four groups of 

 islands, the Madeiran group, the Canaries, the Azores, and the 

 Cape Verdes. 



The Madeiran group contains between 140 and 150 species 

 of MoUusca which ma}^ be regarded as indigenous, the great 

 majority of which are peculiar. Only 

 11 species are common to Madeira and 

 to the Azores, and about the same 

 number, in spite of their much greater 

 proximity, to Madeira and the Canaries. 

 No less than 74 species, or almost 

 exactly one-half, belong to Helix^ and 

 9 to Patida. A considerable number 

 of the Helices are not only specificall}^ 

 but generically peculiar, the genera 

 bearing close relationship to those 

 occurring in the Mediterranean region. 

 As a rule they are small in size, but 

 often of singular beauty of ornamenta- 

 tion. Various forms of Pupa are ex- 

 ceedingly abundant (28 sp.), as is also 

 Ferussacia (12 sp.). There are also 3 Clausilia (which genus 

 occurs on this group alone), and 3 Vitrina (a genus which occurs 

 on all the groups). The land operculates are represented solely 

 by 4 Craspedopoma^ which is common to all the groups except 

 the Cape Verdes. 



The Canaries have about 160 species, only about a dozen of 

 which are not peculiar. As many as 75 of these belong to 



c D 



Fig, 201. — Characteristic land 

 MoUusca from the Madeira 

 group: A, Helix (Irus) laci- 

 niosa Lowe, Madeira; B, 

 Helix {Hystricella) turricula 

 Lowe, Porto Santo ; C, Helix 

 (Iberus) WoUastoni Lowe, 

 Porto Santo ; D, Helix (Coro- 

 naria) delphinuloides Lowe, 

 Madeira. 



