38 Descriptions of Preparations. 



10. Skeleton of Common Feog (Rana Temporaria). 



The following points relating* to the skeleton are common to 

 the entire sub-kingdom Amphibia. Their vertebrae have no neuro- 

 central suture. They have no sternal ribs, nor any representatives 

 of the clavicle and interclavicle of higher and lower vertebrata. 

 Their cervical vertebrae do not exceed two, or at most three, in 

 number, the supra-scapula making its appearance first opposite the 

 second vertebral intercentrum. Their first cervical vertebra differs 

 from that of all higher vertebrata, except a few Chelonia, in re- 

 taining as its centre what is known in them as the odontoid process 

 of the second vertebra ; and it differs from that of all vertebrata, 

 except Mammalia and a few Selachian fishes, in having two lateral 

 articular facets for articulation with the occipital bone, which latter 

 bone rarely possesses even a rudimentary centrum, and never any 

 spine. There is a common suspensorium, as in nearly all fishes but 

 in no higher vertebrata, for both the hyoidean and the mandibular 

 apparatus; and there is no natural division between the suspen- 

 sorial and the palato-quadrate cartilages. The long bones and 

 some others may have epiphyses ; the terminal limb-segments are 

 never more than pentadactylous. 



The following points in the skeleton of Rana are common, prob- 

 ably, to the entire order Anura. The number of their free vertebrae 

 is small, being nine in the Raninae, and most members of the 

 order, but falling occasionally as low as seven ; the coccygeal style, 

 however, which is not reckoned in this numeration, represents at 

 least more than two fused primordial vertebrae. The vertebrae are 

 procoelian ; with the exception of the first, they all have long 

 diapophyses which carry cartilaginous rib -rudiments ; the diapo- 

 physis of the third vertebra expands distally and carries a hammer- 

 shaped cartilage behind which the anterior lymphatic heart lies on 

 the inner surface of the thoracico-abdominal cavity. In Anura 

 alone is the supra-scapula ossified both by ectostosis and endostosis. 

 The OS pubis is of a triangular shape and enters into the formation 

 of the acetabulum together with the ischium and ilium; it may 

 be indurated by the deposition of calcareous salts, but it is never 

 converted into true bone. By apposition of each pubis and ischium 

 with its fellow of the opposite side, and with each other, a vertical 



