MORPHOLOGY OF CYPRINODONT FISHES. 7 



between tlie end of the rib and the postei'ior face of the de- 

 curved part of the transverse process. A mass of cartilage, the 

 anteplenral cartilage (ci]).), lies in front of the distal ends of this 

 pair of ribs and embraces them laterally ; this mass is to a large 

 extent comjDosed of parenchymatous cartilage, but in the centre 

 approaches true hj^aline cartilage in structure (cf. text-fig. 4, B). 

 Axial bone of the priapium. — This extends nearly the whole 

 length of the priapium ; in fi'ont of the articulation of the cten- 

 actinium it has the form of a rod of cartilage enclosed in a cylinder 

 of bone (PL III. A, a.) that bears certain crests and ridges, nainely, 

 (1) the anterior I'idges, the upper (ar.) vertical, the lower (ar.') 



Text-fiofure 4. 



-—apm. 

 --IS. ' 



Neostethus lankesten, $ . Transverse sections ( X 18) : A, tlirough postorbital 

 part of head and base of pulvinular appendage ; B, through second vertebra and 

 anteplenral cartilage. 



ao., aorta ; g., glandular groove ; pva., pulvinular appendage ; a., axial bone ; 

 w., infrasulcar bone; ctm., ctenactinial muscle; pm., muscle of proctal side; 

 apm., muscles of aproctal side ; ppm., pleuro-priapial muscle ; ac, antepleural 

 cartilage ; r., priapial rib ; re, cartilage ; tr., transverse process of third 

 vertebra ; k., kidney ; ce., oesophagus ; so., sinus venosus. 



nearly horizontal and aproctal ; these increase in height back- 

 wards and end abruptly at the level of the pulvinular spine. 

 (2) The main crest {cr.) : this rises obliquely from the proctal 

 side of the axial bone and then curves upwards until it is 

 vertical (text-fig. 4 A, a.) ; it commences a little behind the end 



