MONOTREMATA. 
10 
running along the upper surface of which is the clavicle; the 
space below the lateral branches on either side almost entirely 
occupied by ft large flattened cpicomcoid, which is bounded on 
the outer side by a coracoid bone; the jaws edentate, or provided 
with crushing teeth of a horny nature. The mammary glands 
abdominal, in the form of numerous elongated subcylindrical 
lobes, converging and opening into a small oval areola, which lifts 
not been seen to form a projecting nipple; ccrcura small; facial 
bones produced and covered by a hairless skin ; ear without any 
external concha; young (in Ornithorbyuchus at least) naked. 
The section Monotremata contains but two well-determined 
species, both of wiiicli are from Australia, und were originally 
described by Dr. Shaw towards the close of the last century,— 
the one under the name of Myrmccophnga aculeata , and 
the other under that of Platypus anatinus. The former, in 
many modem systematic works, appears under the name of 
Echidna hystrir ; and the latter with the name Ornitho 
rhynchus paradoxus, —a name first applied, in 1800 , by 
Blumenbach. 
An animal presenting such a remarkable combination of 
characters as the Omithorhynchus, could not fail soon to 
attract the attention of the anatomist and physiologist, and 
since it was soon discovered to approach the oviparous classes 
of birds and reptiles in many of its characters, a question 
arose as to whether, like the Mammalia, it suckled its young, 
or, like the other two classes just mentioned, was oviparous. 
Even after the Omithorhynchus had been carefully dis¬ 
sected by Meckel 1 , that able anatomist, who had discovered 
and well described the mammary glands, still doubted whether 
the animal might not lay eggs, inasmuch as the generation 
of the Marsupialia closely resembled that of the oviparous 
' Scehb Omithorhynchi paradoxi detcriptio ansi arnica , folio, 182G; and 
Bcitrage zur Vergteichenden Anatomic, 1808. 
