CANARIAN GROUP. 303 



tornatellina, Lowe ; an ' Achatina ' which abounds in the Ma- 

 deiras, and a single example of which was met with by Mr. 

 Watson a few years ago in Grand Canary. (20) Limncea 

 truncatula, Mull. ; likewise common at Madeira, but found 

 by Mr. Watson in the Canarian archipelago. And (21) Assi- 

 minea littorina, Delle Chiaje ; a European, submarine species, 

 abundant at Madeira and the Salvages, which was obtained by 

 Mr. McAndrew in Teneriffe. 



After making these various additions to, and deductions 

 from, the local catalogue as given by Mousson, it will be seen, 

 by a reference to the list at the close of the present Section, 

 that the true species (whether indigenous or introduced), so far 

 as I can understand them, which I should be inclined to 

 acknowledge as Canarian, amount to 189; and it is somewhat 

 remarkable that it should happen to be a little in advance of 

 the number which is indicated (namely 176) in the very much 

 more perfectly explored Madeiran Group. This fact however 

 must not be permitted to leave the impression that the Canaries 

 are better stocked as regards their Pulmoniferous Mollusks than 

 the Madeiras ; for it should be borne in mind that the former 

 are made up of seven large islands, the central one of which 

 rises to an altitude of more than 12,000 feet, whereas the latter 

 (the loftiest point of which is only 6,000) have but five islands, 

 or if we count (as is most natural) the rocks of the Desertas 

 as one, merely three. Hence the circumstances are very differ- 

 ent a priori, and 176 species at the Madeiras imply a very 

 much more redundant fauna than 189 do at the Canaries. 

 Added to which, the Madeiran catalogue embraces an immea- 

 surably larger proportion of extra forms which (on account of 

 their having been treated as only well-marked varieties rather 

 than as separate species) are altogether lost sight of in a mere 

 numerical enumeration, the ' species,' as technically and 

 rigidly understood by that term, being the only organisms 

 which it is the custom to register under distinct numbers in a 

 geographical catalogue. But although acknowledged as ' varie- 

 ties ' rather than as species, it does not necessarily follow that 

 some of them may not in reality tally better with what we 

 believe to be the latter, or at all events that they may not have 

 an equal importance with many of the forms at the Canaries 

 which (through the want perhaps of sufficient material from 

 which to judge) have been accepted unreservedly as species. So 

 that^from this point of view likewise (indeed I might almost 

 say a fortiori) the Madeiran catalogue can hardly fail to be 

 recognised as a much richer one than that of the Canaries, 

 numbering, when all the forms, as hitherto acknowledged, are 

 taken into account, no less than 246, against only 224 which 



