1870.] MR. HUDSON ON THE BIRDS OF BUENOS AYRES. 545 
chechus rosmarus). After a preliminary notice of the labours of 
Daubenton, Home, Von Baer, and others, he proceeded to treat 
on the outward characteristics of the young male Trichechus which 
the Society possessed in 1867. Dwelling respectively on the colour, 
general configuration, manner of walking, skin-folds, and head, he 
closed this section by a careful study of its pectoral and pelvic limbs 
as compared with those of Phoca. With a few remarks on viscera 
and genital organs, he more fully described the vascular channels 
and the vocal organs, verifying Von Baer’s observation as to the 
diminutive size of the epiglottis. Of the myology nothing hereto- 
fore has been known save Sir Everard Home’s incidental notice of 
the Walrus possessing well-developed interossei. Dr. Murie having 
dissected somewhat minutely the fleshy structures, proceeded to 
point out that though the genera Trichechus, Otaria, and Phoca 
manifest considerable variety in form, gait, and degree of limb-move- 
ment, they, nevertheless, muscularly present general agreement. In 
the presence of a coraco-brachialis, a flexor brevis manus, a pronator 
quadratus, an opponens pollicis, and a palmaris brevis, the Walrus is 
differentiated from the Eared and Earless Seals. Though deficient 
in concha, the auricular muscles are remarkably large. ‘There is an 
external anconeus as in Ofaria; and, as in it and Phoca, there are a 
double set of extensors of the manus. Compared with Seals, there 
are two extra peronei and a flexor brevis hallucis. 
This paper will be published in full in the Society’s ‘ Transactions.’ 

The following (5th and 6th) letters on the ornithology of Buenos 
Ayres*, addressed to the Secretary by Mr. W. H. Hudson, C.M.Z.S., 
were read :— 
(No. V.) 
“ Buenos Ayres, March 22, 1870. 
*“« My pear Srr,—In a letter, dated a few days back, I gave you 
some account of the Tenioptera varicgata. This bird, a Plover in 
habits and a Thrush in appearance, finds a congenial habitat in this 
part of the country when the cold compels it to forsake the barren 
plains of Patagonia. Before winter sets in, the giant thistles that 
cover the plains in summer dry up and crumble to dust, and, the 
grass being eaten down very close by the innumerable flocks of sheep, 
the earth presents all the smoothness so agreeable and so necessary to 
this species. ; 
“ Even at night they do not seek for shelter, as do the Trupials, 
Anthi, and other passerine birds that roost on the ground, but, 
Plover-like, remain on the bare level places they frequent. I do not 
recollect ever having met them on the grassy pampas west of the 
Buenos-Ayres frontier. As they do not perch on reeds, they would 
naturally avoid such places, preferring the inhabited districts. Thus 
the settlement of the country has been favourable to this species, as 
it has to the Biscacha, the Burrowing-owl, and the Véru-téru. 
* For Mr. Hudson’s last letter, see P. Z, 8. 1870, p. 332. 
