INTRODUCTION. xiil 
The remarkable distribution of some of the higher animals, such as the Prosimiw 
among mammals, the Ratite among birds, the Crocodilide among reptiles, is well 
known, and every student of terrestrial Invertebrata who has paid some attention 
to the geographical distribution of his favourite group must be acquainted with similar 
facts. I may be allowed here to mention the Gasteropod genus Clausilia, the Nenia 
group of which is now limited to the high valleys and mountain chains of Peru, 
Ecuador, and Colombia, and, with one species only, to the island of Puerto Rico, 
and which has its nearest allies not in the New, but in the Old World, in the Lami- 
nifera group (Neniatlanta, Bgt.), which now lives on the top of La Rhune, a mountain 
near the coast of the Bay of Biscay, and in the Garnieria group, the members of 
which inhabit the mountainous districts of China, Siam, and Cambodia. On some 
pieces of bark in the virgin forests of the Pacific slope of Guatemala I discovered a 
new species of Diplommatina *, a Gasteropod type, the autochthonous members of 
which had previously only been known from India and the neighbouring archipelagos. 
In the woods near Retalhuleu (N.W. Guatemala) I found a new species of the 
Myriopod genus Polyxenus, the type of which is the well-known P. lagurus, L. 
Another species of this well-defined Chilognath genus has been mentioned by 
Mr. Humbert from Ceylon, and one species has been described from North America 
by Say. A not less characteristic Myriopod type, the genus Siphonophora, abounds 
under the bark of the fir trees near the summits of the volcanos Agua and Fuego in 
Guatemala, whilst a nearly allied species has been found in Madagascar by my friend, 
Prof. C. Keller. Another species has been described from Ceylon by Mr. Humbert. 
In the woods of the Volcan de Agua, at an elevation of about 10,000 feet, I met 
with a species of land-leech belonging to the genus Cylicobdella, Grube, which is 
closely allied to, if not identical with, C. lumbricoides, Gr., discovered by Prof. Fritz 
Miiller at Desterro in Brazil. 
Similar instances of an almost world-wide distribution might, no doubt, be found 
among other groups of Invertebrata whose facilities for active or even passive 
migration are very limited. 
Unfortunately our present knowledge of the Acarids is too fragmentary to allow 
any more definite speculations as to the phylogeny of this group. Whether 
it is, geologically speaking, as ancient as some other groups of the Arachnida, or 
* This species has since been described and figured as Diplommatina stolli in the ‘ Biologia Centrali- 
Americana’ (Mollusca, p. 20, Tab. I. figg. 19a, 6), by Prof. E. von Martens. 
