10. An abdominal vertebra of a Sturgeon (Afipenttr Stvrio), showing the centrum 



or body still represented by a segment of the persistent continuous noto- 

 chord : the inner layer of the fibrous capsule of the notochord has increased 

 in thickness, and assumed thu texture of tough hyaline cartilage. In the 

 outer layer are developed distinct, firm, and opakc cartilages the ncurapo- 

 physes, which consist of two suporim]x>scd pieces on each side, the basal por- 

 tion bounding the neural canal, the apical portion the parallel canal filled by 

 fibrous elastic ligament and adi|>ose tissue : above this is the single cartila- 

 ginous neural spine. The para|K>physes arc now distinctly developed, and 

 joined together by a continuous expanded base, fonning an inverted arch be- 

 neath the notochord, for the vascular trunks. Short and simple plcurapo- 

 physes are articulated by ligament to the ends of the laterally projecting 

 parapophyses. There is a small accessory (intcrneural) cartilage at the fore 

 and back part of the base of the ncurapophysis , and a similar (interlurmaJ) 

 one at the fore and back part of the parajxiphyscs. 



Prepared by Mr. George Jlansbrov, Anatomical Student. 



11. A section of the abdominal part of the vertebral column of the Lfpidorire* 



aiinfctfju. The continuous notochord still represents the vertebral bodies, 

 but its capsule is thickened. The neurapophyses, the neural spine, and the 

 parapophyses are ossified ; the latter arc of great length, and resemble ribs, 

 but there arc no true or distinct plcurapophyscs, as in the Sturgeon or Siren. 



Prepared by Prof. Otcen. 



12. A series of the semi-ossified portions of the vertebral bodies of the Spotted Dog- 



fish (Scyllium Ca*icu/a) -. they consist each of two conical pieces confluent at their 

 apices, which ore perforated : each cone forms a concave articular extremity of 

 the vertebral body, which contained a remnant of the primitive gelatinous 

 notochord. This was continued through the central perforation, and had been 

 reduced by the ossification of the biconical plates to a moniliform figure, or 

 chain of semifluid gelatinous beads. The exterior of the ossified part of each 

 centrum was occupied by a clear cartilage developed from the primitive fibrous 

 capsule of the notochord. Iluntcrian. 



18. A vertebral centrum of the Porbeagle Shark (Lamna contained). Ossification 



B 2 



