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tebrae in the Ornithorhynchus ; six, including the first, have haemapophyses and haemal 

 spines, and the haemapophyses are ossified along their sternal halves ; those of the succeed- 

 ing ribs, as far as the fifteenth, are cartilaginous, much expanded, and overlap one another 

 like broad scales ; the last two pairs of ribs are free or floating. Most of the vertebral 

 ribs have undergone a slight displacement forwards, and articulate over the interspace of 

 their own and the antecedent centrum. This character of a greater or less number of 

 the ribs is constant in the Mammalia. The vertebrae without moveable ribs that inter- 

 vene between the dorsals and the anchylosed mass forming the sacrum are called 'lumbar 

 vertebrae ' ; they are two in number in the Ornithorhynchus, There are also two sacral ver- 

 tebrae, and twenty caudal vertebrae ; these are remarkable for the length, breadth, and flat- 

 tened or depressed character of their transverse processes, which cease to be developed only 

 in the last vertebra ; they support at an early period of life distinct rudiments of ribs at their 

 extremities. The dorsal nerves perforate the neural arch directly : the cervical and lumbar 

 nerves pass out by the intervals of the neurapophyses. The scapulae are compressed curved 

 plates, vertical in position, like the other pleurapophyses : they have coalesced with their 

 haemapophyses, the ' coracoids,' which articulate below to the modified haemal spine, called 

 ' episternum,' and also with the succeeding spine, called 'manubrium,' or first bone of the 

 true sternum. Two plates of bone dismemberments of the coracoid, but attached along their 

 anterior borders extend their attachments also to the elongated T-shaped episternum. The 

 clavicles are two curved styles, extending from the acromion to the upper transverse bar of 

 the episternum. The humerus is remarkable for its shortness and breadth, especially of its 

 two extremities. There is a small sesamoid ossicle above the internal tuberosity, answering 

 to the capsular ossicle in the shoulder-joint of birds : the inner condyle is perforated. The 

 ulna is equally remarkable for its large and transversely extended olecranon. There are five 

 digits : the first, or inner one, with two phalanges ; each of the rest with three ; a numerical 

 arrangement which is tolerably constant in the Mammalian Class. The femur is short, broad 

 and flattened, but less powerfully developed than the humerus. The fibula strikingly resem- 

 bles its homotype, the ulna, by its superior length to the tibia, and especially by the great 

 development and terminal expansion of the process answering to the olecranon which extends 

 above and behind its proximal articulation with the femur. In this skeleton, which has 

 belonged to a male, is shown the singular spur-like perforated ossicle articulated to the acces- 

 sory tarsal bone behind the ankle-joint. The digits of the foot are the same in number, and 

 have the same number of phalanges as those of the hand. 



The ilium, ischium, and pubis have coalesced, and the symphysis of the pubis and isclfium 

 is obliterated. Two moderately long and broad marsupial bones are articulated to the brim 

 of the pelvis, and the pubis sends out two processes near its proximal end. In all the chief 

 essential characters of the skeleton, as the double occipital condyle, the convex condyles of 

 the lower jaw and their articulations with the squamosals, the number of cervical vertebra; 

 (seven), the flattened articular surfaces of the centrums of the vertebrae joined by the inter- 

 vertebral cushions, and the numbers of the phalanges of the digits of the fore and hind feet, 

 the mammalian nature of the Ornithorhynchus is manifested : but the flattened eden- 

 tulous fore part of the jaws, the small, smooth and sutureless cranium, the persistence of the 

 articulations of the second cervical ribs, the fully developed coracoids and epicoracoids with 



