402 I>A VISON. [Vol. XI. 



Axial Skeleton and Appettdages. 



The vertebrae are only partially ossified. The transverse 

 processes are wholly cartilaginous, and a portion of the inter- 

 nal part of the body of the vertebrae is unossified. The carti- 

 laginous posterior projection of the roof of the spinal cord is 

 invested with a thin parostosis. The cartilaginous intercentra 

 are present. The ribs are present as cartilage. The neural 

 and diapophysial spines are imperfectly developed. The hypa- 

 pophyses are well marked. The shoulder girdle is wholly car- 

 tilaginous, and presents elements of scapula, coracoid and pre- 

 coracoid. The scapula is exceedingly thin, being only two 

 cells in thickness. The other elements are correspondingly 

 slender. No sternum is present. The humerus is covered with 

 a thin layer of bone, except in the regions of the extremities. 

 The radius and ulna are also ossifying externally. The carpus 

 is present as pure cartilage, and the phalanges remain as hya- 

 line tissue also. The pelvic girdle is entirely cartilaginous. 

 All the elements are present as in the adult, but there is no 

 evidence of the posterior bony disc. The femur is invested 

 with a very delicate ectostosis in the shaft region. The future 

 prominent trochanter process is indicated by a slight flexion 

 of the cartilage at that point. The two abductor, the adductor 

 and two rotator muscles have the same locations as in the 

 adult. The tibia, fibula, tarsus, metatarsus, and phalanges 

 show no signs of ossification. This affords weighty evidence 

 that the formation of the anterior limbs is in advance of the 

 posterior. 



I have not been able to discover any conical arrangement in 

 the fibres of the dorsal muscles. The abdominal muscles have 

 the same relative dispositions as in the adult. The transver- 

 salis is unaffected by the inscriptiones tendineae, and arises 

 from the internal plate of fascia, originating in common with 

 the external plate on the neural spine. The digestive, respira- 

 tory and excretory systems correspond with those of the adult. 

 Having described the anatomy of these different individuals, 

 it remains to determine the genealogical status of Atnphiimia 

 among vertebrates. 



