Correspondence—Mrs. Ayrton. KS HE 
1. The recent Indrisine Chiromys, Mesopropithecus, Paleopropithecus, 
Archeolemur, and Hadropithecus are all more or less specialized repre- 
sentatives of one common Prosimian stock. 
2. Specialization has taken place in various directions and to very 
varying degrees among the different genera enumerated ; Archeolemur, 
Hadropithecus, and Mesopropithecus retaining on the whole the greatest 
number of pithecoid characters. 
3. Even the least specialized forms have undergone retrogressive 
changes as compared with the ancestral Tertiary stock from which 
they, in common with the extant Indrisine, are derived. This is 
notably true as regards the condition of the frontal region of the brain. 
4. A comparison of the least specialized members of this Indrisine 
group of Prosimize with the various families of the Old and New 
World Monkeys, shows in several characters closer affinities with the 
latter than with the former (e.g., auditory bulls, traces of primitive 
dentition, procumbent lower incisors, tendency to lose third molar, 
platyrhine condition of nasals). 
5. A comparison of the Malagasy Lemurine, recent and sub-fossil, 
with the various genera of the Indrisine group supports the belief that 
retrogressive specialization has proceeded even further in their case 
than in that of the recent Indrisine. This retrogressive specialization 
has in general proceeded on similar linesin the two groups, though the 
deviations from the primitive dental formula are less pronounced 
among the Lemurine than among the Indrisine genera, 
6. The members of the family of the Lemuride outside of 
Madagascar are found in scattered groups over a wide area in the Old 
World and bear the marks of a decadent group. All are nocturnal, 
and many are curiously specialized. 
7. A comparison of the various genera of Lemuride with one 
another and with the New World Monkeys, both recent and fossil, 
leads to a strong presumption that these families as well as the 
Malagasy Indrisine group have had a common origin. 
8. In view of the recent additions to our knowledge of the Prosimiz 
and of their close relations to the Apes, it seems no longer necessary, 
or indeed possible, to separate the Primates into the two suborders of 
Lemuroidea and Anthropoidea. 
Most of the specimens described by Mr. Standing belong to the 
Malagasy Academy, Antananarivo, but a typical and extensive 
selection has been acquired by the British Museum (Natural History). 
CORRESPONDENCE. 
st 
MARINE RIPPLE-MARK. 
Str, —In your issue for February, p. 96, your correspondent 
Mr. A. R. Hunt quotes one among the many experiments I showed 
in my lecture to Section G at Cambridge, and deduces from it that 
my ‘‘results and conclusions . . . . have practically no bearing 
on the phenomena of the sea-shore and sea-bottom.”’ 
Even had I shown only this one experiment, such a statement 
would surely have been somewhat sweeping; but as I actually 
