4i6 



THE ANIMAL KINGDOM. 



size in the two first-named orders, and the right and left parts are either 

 continuous ventrally or united by ligament. A distinct supra-scapula is 

 present in many Elasmobranchii, especially in Rays, where it is attached to 

 the vertebral column, and in the Sturgeon, which has also a large clavicular 

 process. The form of the parts varies much, e.g. in Rays the articular 

 region is of great extent and much fenestrated. The bones are small in 

 Teleostei, and there are many variations in their mode of ossification. The 

 Ganoidei and Teleostei have investing bones known as supra-clavicle, 

 clavicle, inter-clavicle, and post-clavicle, all derived apparently from the 

 skin and lining membrane of the branchial cavity, and present in none of 

 the higher Vertebrata (p. 97) ; and a supra-temporal scale-bone (the first of 

 the lateral line) connects the clavicular series to the epi- and opisth-otic 

 regions of the cranium. There are two investing bones also in Dipnoi, 

 which ensheath the cartilage in Protopterus and Lepidosiren. The girdle is 

 deeply imbedded in the muscles in the two last-named Fish, and the limb 

 is articulated to its proximal, i.e. dorsal, extremity. 



The pelvic cartilage is a continuous curved bar in Elasmobranchii, 

 representing an ischio-pubic region, the part dorsal to the attachment of 

 the limb, i. e. the iliac region, being absent or inconspicuous ; but it is large 

 in Holocephali, where the two halves of the girdle are united ventrally by 

 ligament. Two minute cartilages are found in Polypterus : otherwise the 

 pelvis is not represented in any Ganoid or Teleostean. A median cartilage 

 bears the limbs in Dipnoi, and extends forwards as a pointed rod. 



The fore-limb consists typically in Elasmobranchii of three basal 

 cartilages, pro-, meso-, and meta-pterygium, articulating each with a 

 facet on the shoulder-girdle ; of one or two outer rows of cartilaginous 

 rods known as radialia, followed by horny fin-rays. The pro- is sometimes 

 not differentiated from the meso-pterygium. Certain radialia intrude in 

 Rays between the meso- and meta-pterygium, touching the shoulder-girdle. 

 Polypterus among Ganoidei has rod-like ossified pro- and meta-pterygia and 

 a broad meso-pterygium. All other Ganoidei and Teleostei have a meso- 

 pterygium generally imbedded in the base of the first fin-ray, some intrusive 

 radialia and a meta-pterygium. But this region of the limb may be entirely 

 absent in some Teleostei. The radialia are well-developed in chondrostean 

 Ganoidei and Polypterus ; they are usually small and nodular in Teleostei, a 

 group in which movement of the limb takes place along the line of union 

 between them and the more proximal parts. The fin-rays are ossified in 

 Ganoidei and Teleostei, usually soft, sometimes entire, especially in the first. 

 The hind-limb in Elasmobranchii and the Holocephali contains often only 

 one basal cartilage, a metapterygium, but a second is sometimes present in 

 the former, and is usually termed pro-pterygium. It probably represents 

 an undivided pro- + meso-pterygium. There are radialia and fin-rays, as 

 in the fore-limb. The most posterior fin-ray is usually large, and con- 



