MADEIRA AND THE CANARIES 



297 



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

 Europe. 



Twenty-six species of univalve Mollusca, the majority being 

 modified forms of Hydrolia, have been described from the Caspian, 

 namely, Micromelania (6), Caspia (7), Clessinia (3), Nematurella 

 (3), Litlwglyphus (1), Planorhis (1), Zagrahica (1), Hydrohia (2), 

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

 (Didacna, Adacna, Monodacna), which also occur in estuaries 

 along the north of the Black Sea. A form of Cardimn 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. 



(d) The Atlantidcan ])rovince consists of the four groups of 

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

 Cape Verdes. 



The Madeiran grou'p contains between 140 and 150 species 

 of Mollusca which may lie regarded as indigenous, the great 

 majority of which are peculiar. Only 

 1 1 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. 

 Xo 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 specifically c 



liut generically peculiar, the genera Fig. 201.— Characteristic land 

 1 • 1 1 i.- 1 • J. J.1 Mollusca from the Madeira 



Ijearing close relationship to those 



group: A, Helix [Irus] Jaci- 

 niosa Lowe, Madeira ; B, Helix 

 {Hystricclla) turricnlfi Lowe, 

 Porto Sauto ; C, Helix{Iberus) 

 Wollastoni Lowe, Porto Santo ; 

 D, Helix (Coronaria) deljplu- 

 nuloides Lowe, Madeira. 



occurring in the Mediterranean region. 

 As a rule they are small in size, but 

 often of singular beauty of ornamenta- 

 tion. Various forms of Fwpa are ex- 

 ceedingly abundant (28 sp.), as is also 



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

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

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

 hj 4 Ci^aspedopoma, 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 



