182 ANATOJIY OF VERTEBRATES. 



Ijasis, 64, for muscular attachments, became co-expanded ; the 

 ischia also, 63, assumed the form of flattened triangular plates ; 

 and the ilia, though still ' long bones,' were stronger, and attached 

 by ligament to the riblets of one or two vertebra3 ; and these, in 

 Nothosaurus, became expanded for more effective fixation of the 

 pelvic arch. A ' tarsus,' 68, and ' metatarsus,' are now definable ; 

 and the ' digits,' with fewer joints, do not exceed five in number. 

 All the bones are solid in both IclttJii/o- and Sauro-pterygia. 



From the Sauropterygian type of pelvic arch and limb, the 

 transition is easiest to that in the marine Chelurda of the j^resent 

 day. But the course of developement from the Proteus will Jae 

 here resumed and traced to the saltatory grade which the hind- 

 limlj acquires in the Batrachian order. 



Amplduma tridactylum, with proportionally shorter hind-limbs 

 than in Protevis (fig. 101, d), has them terminated by three toes. 

 Menohranchus shows four toes : and Menopoma five, which is the 

 numljcr usual in the hind-limbs of Newts and Salamanders. In 

 Mmopoina, fig. 43, the sacral vertebra, ,?, has a longer and 

 stronger transverse process, t, and riblet, pjh than the vertebras 

 before and behind ; and pi is united to the cartilaginous elements, 

 63 and 64, closing the inverted arch by the ri))-like continuation, 62. 

 To the lower end of this simple 'ilium' and conjoined part of the 

 ' ischio-pubic ' cartilage is ligamentously attached the short and 

 simple femur. To this succeeds a shorter tibia and fibula — the 

 latter reminding us of the plesiosaurian fibula, by its outward 

 curve. The tarsus is cartilaginous in Menopoma ; the metatarsals 

 support 1, 2, 3, 3, 2 phalanges, resj)ectively, from the innermost, I, 

 to the fifth, V. The toes are webbed to near the last joint. Every 

 joint in the limb is syndcsmotic, and the ossification of the bones is 

 limited to an outer crust, covering persistent solid cartilage. In 

 the dccomj^osing body this dissolves away ; and if the ossified 

 parts Ijccome petrified, the fossil lione appears to have had a large 

 medullary cavity. 



In the Land-salamander the broad ischio-pubic plate, fig. 113, 

 , „ liecomes ossified at h, hwi remains cartila- 



ginoiis at the angles c, and the symphysis ; 

 whence it extends forward, and bifurcates, 

 as at d, representing the last pair of abdo- 

 minal ribs in higher reptiles. There is a 

 vasevdar perforation in eacli pubic part of 

 tlio ])late. Tlie ilium, a, retains its siniiile 

 rih-like character. 

 Tlic Ta(li«ilc, fig. 42,afi['ords a significant example oi' the trans- 



