v. ] SKELE TON OF LO IVER LIMB. 193 



bably a pair of ischia. These are long and slender bones 

 detached from each other as well as from the vertebral 

 column. 



This ischium may be elongated, produced backwards (i.e. 

 post-axially) and downwards, and separated from its fellow in 

 the middle line ventrally, as in all Birds except the Rhea, 

 in which latter these bones bend upwards and meet at their 

 distal ends. 



The ischium of Birds generally anchyloses more or less 

 with the posterior part of the very elongated ilium. 



In Reptiles the ischio-pubic bone generally meets its fellow 

 in a ventral symphysis. It may do so when the other ventral 

 elements do not so meet. Such is the case, e.g., in the Snake 

 Stenostojna. On the contrary, it may fail so to meet its 

 fellow, although the other ventral elements effect a junction. 

 We find this condition, e.g., in the Lizard Seps. Often, as 

 e.g. in the Boa, the bone may be represented by a mere 

 cartilaginous rudiment. 



''-, 



FIG. 165. SKELETON OF RUDIMENTARY PELVIC LIMB OF BOA CONSTRICTOR. 

 (After Fiirbringer.) 



l r , rudimentary femur, at the end of which is (t) a minute, triangular, and hook-like 

 tibia; i, so-called pubis- possibly an enormous ilio-pectineal eminence: /, 

 rudimentary ilium ; p, ischium or pubo-ischium. 



A tuberosity of the ischium generally exists in Lizards ; this 

 does not, however, anchylose with the vertebral column, but 

 is connected by a strong ligament with the hinder end of the 

 ilium, which ligament answers to the great sacro-sciatic liga- 

 ment of man. 



In Tailed-Batrachians the ischio-pubic bone or cartilage is 

 a large lamelliform expansion with an elongated symphysis. 

 It may form one single cartilaginous undivided plate, as in 

 Proteus. In Frogs and Toads the ischia are small, lamelli- 

 form, and so closely applied and anchylosed together as to 

 be, as it were, all symphysis. 



In Fishes the ossa innominata have already been noticed, 

 and they consist probably of ischio-pubic bones or cartilages 

 only. We here, however, often meet with an anomaly of 

 connexion not found in any higher class. Thus we find the 

 innominate bones in many cases directly connected with the 



O 



