The Value of Fossils 331 
the offered solutions. The mere fact of palms having flourished in 
Miocene Spitzbergen led to an hypothetical shifting of the axis of 
the world rather than to the assumption, by way of explanation, that 
the palms themselves might have changed their nature. One of the 
most valuable aids in geological research, often the only means for 
reconstructing the face of the earth in by-gone periods, is afforded by 
fossils, but only the morphologist can pronounce as to their trust- 
worthiness as witnesses, because of the danger of mistaking analogous 
for homologous forms. This difficulty applies equally to living groups, 
and it is so important that a few instances may not be amiss. 
There is undeniable similarity between the faunas of Madagascar 
and South America. This was supported by the Centetidae and Den- 
drobatidae, two entire “families,” as also by other facts. The value 
of the Insectivores, Solenodon in Cuba, Centetes in Madagascar, has 
been much lessened by their recognition as an extremely ancient 
group and as a case of convergence, but if they are no longer put 
into the same family, this amendment is really to a great extent due 
to their widely discontinuous distribution. The only systematic 
difference of the Dendrobatidae from the Ranidae is the absence of 
teeth, morphologically a very unimportant character, and it is now 
agreed, on the strength of their distribution, that these little arboreal, 
conspicuously coloured frogs, Dendrobates in South America, Mantella 
in Madagascar, do not form a natural group, although a third genus, 
Cardioglossa in West Africa, seems also to belong to them. If these 
creatures lived all on the same continent, we should unhesitatingly 
look upon them as forming a well-defined, natural little group. On 
the other hand the Aglossa, with their three very divergent genera, 
namely Pipa in South America, Xenopus and Hymenochirus in Africa, 
are so well characterised as one ancient group that we use their 
distribution unhesitatingly as a hint of a former connection between 
the two continents. We are indeed arguing in vicious circles. The 
Ratitae as such are absolutely worthless since they are a most 
heterogeneous assembly, and there are untold groups, of the arti- 
ficiality of which many a zoo-geographer had not the slightest 
suspicion when he took his statistical material, the genera and 
families, from some systematic catalogues or similar lists. A lament- 
able instance is that of certain flightless Rails, recently extinct or 
sub-fossil, on the islands of Mauritius, Rodriguez and Chatham. Being 
flightless they have been used in support of a former huge Antarctic 
continent, instead of ruling them out of court as Rails which, 
each in its island, have lost the power of flight, a process which 
must have taken place so recently that it is difficult, upon morpho- 
logical grounds, to justify their separation into Aphanapteryx in 
Mauritius, Erythromachus in Rodriguez and Diaphorapteryx on 
