\M) .MAMMVKY PCETUS OF THE BCinDXi KYSTRIX. 
077 
A warm-blooded air-breather, compelled to seek its food in water, could not safely 
carry the progeny it had brought forth in a pocket beneath its body during such quesl ; 
and all observers have noted the nest-making instinct of the Vlatfffpv^ in which tempo- 
rary and extraneous structure's only the young have hitherto been found *. Mr. ( i borge 
Bennett states that the nest "appears to he found about the time of bringing forth the 
young, and consists merely of dried grass, weeds, &c."f 
Whether tin 1 Echidna prepares any extraneous nest, is net known. The specimen 
transmitted to me by Dr. MlJELLEE was caught in the hollow of a prostrate M cotton tree." 
Being a terrestrial annual, she can carry her young about habitually concealed or partly 
sheltered in her pouches; and the present observations show tin 1 nearer affinity in tins 
respect of tin 1 Echidna to the marsupial Lyencephala, The Echidna may further mani- 
fest this relationship by the more minute size of the young when horn and transferred 
to the pouch, as compared with the Ornithorhynchus ; but the size of the new-born or 
newly-excluded young of that monotreme is unknown. The smallest specimen of a young 
Ornithorhynchus which I have yet seen is that (Plate X Id. tig. 5) to w hich allusion has 
been already made as being about, two inches in length in a straight line. 
The following are tin 1 comparative dimensions of this, and of the young of the female 
Echidna (ih. fig. 3 (magn.), Plate XL. figs. 6-10 (nat. size)), the subject of the present 
communication : — 
Young 
Viiung 
Ornithorhynchus. 
Ed 
tidha. 
in. 
lin. 
in. 
lin. 
Length from the end of the upper jaw, over thecurveof 
the back, to the end of the tail . 
3 
9 
1 
Ill 
Length from the same points in a straight line 
along the 
9 
1 
L 
1 
Greatest circumference of the body . 
9 
9 
1 
0 
8* 
0 
4 
Length of the upper mandible from the gape 
0 
o 
O 
0 
n 
Breadth of the upper mandible at the base 
0 
4 
0 
i 
o 
0 
0 
i 
0 
4 
0 
1 
2 
0 
3 
0 
2 
0 
H 
0 
14 
0 
4 
0 
l 
0 
3 
0 
H 
The circumstances under which this young Echidna was obtained are given in a letter 
by the captor, Mr. G. 0. Harris, to Dr. MuELLEE, dated "Colac forest, August 31, 
18G4." 
* Tom. cit. p. 5;*:*. f Trans. Zool. Soc. vol. i. pp. 217 & 259, 
♦ This might have been more before the body had become somewhat dried, or shrunk in parts. 
