318 



shown. The humerus attains its maximum of breadth in this burrowing Monotreme : the 

 epiphyses at both proximal and distal ends are still distinct, and are subdivided, there being 

 an ossicle for each tuberosity at the proximal end. The base of the enormously developed 

 inner condyle is obliquely perforated : the olecranon is bifid, and less expanded than in the 

 Ornithorhynchus ; but both bones are stronger in the shaft, and the metacarpal and pha- 

 langeal bones are singularly short and thick, and support very long and strong burrowing 

 claws. The articulations remain between the three constituent bones of the os innominatum : 

 the marsupial bones are longer and more slender than in the Ornithorhynchus. The fibula 

 developes a process answering to the olecranon. The short perforated spur-like ossicle, arti- 

 culated to the back of the tarsal joint, indicates the sex of the individual to which this skele- 

 ton has belonged. The innermost toe or hallux is very short ; the second is the longest toe ; 

 the other three toes gradually decrease in length. The calcaneum sends forwards a short 



thick process like a sixth toe. 



Mm. South. 



1705. The skull, wanting the lower jaw, of the Echidna Histrix. 



Presented by Ronald Gunn, Esq. 



1706. The skull of an Echidna, partially disarticulated. 



Presented by Prof. Owen, F.R.S. 



1707. The anterior part of the cranium of an Echidna, bisected horizontally to show 

 the extent and complexity of the superior part of the turbinal capsules of the 

 organ of smell. Prepared from a specimen presented by Dr. Hobson. 



1708. Portions of the skeleton of a young Echidna Histrix. 



These comprise the mutilated trunk, and portions of three extremities. The neurapo- 

 physes of the atlas have not coalesced with each other, and there is no neural spine. The 

 transverse processes have a minute perforation for the vertebral artery. The odontoid is 

 distinct from the centrum of the axis, and articulates largely with the neural arch of the 

 atlas. The body of the axis is still disunited from its neural arch : it sends out a short par- 

 apophysis on each side, and the neural arch developes a deep compressed diapophysis : the 

 pleurapophysis, which articulates with both these processes, is compressed and deeper than 

 it is long : it contributes little to the formation of the vertebral canal, in consequence of the 

 approximation of the ends of those upper and lower transverse processes. The harmonise 

 between the ' head ' of the pleurapophysis and the parapophysis, and between the ' tubercle ' 

 and the diapophysis, continue distinct in the remaining cervical vertebrae ; and the mode 

 of formation of the vertebral foramen, agreeably with the typical composition of the ver- 

 tebra themselves, is instructively demonstrated. The first 'dorsal ' vertebra is characterized, 

 as in the Ornithorhynchus, by the different form and proportions of its pleurapophyses, 

 which join by heemapophyses the sternum. Not any of the cervical vertebrse have zygapo- 



