418 



TRANSACTIONS OF THE AxMERICAN PHILOSOPHICAL SOCIETY 



ently such tubes may serve as a probe for poking into seaweed or into crannies, as among the 

 sessile organisms of a coral reef, in search of minute food. 



In every case the attainment of the specialized position and direction of the mouth 

 has involved the differential growth of all the bones of the jaws and suspensorium. An 

 increase in the length of the gape, involving a lengthening of the jaw, may be effected either 



)^ ^iA[i]u^S ^ 



D Lepidosteus 



B Semlonotas 



A Acentrophorus 



Fic. 287. Forward swing of the suspensorial line (HQ) in holosteans. A. Acentrophorus. After E. L .Gill. B. Semionolus. 

 After A. S. Woodward. C. Lepidotus. After A. S. Woodward. D. Lepidosteus. 



by moving the quadrate-articular facet (0 downward and backward (Figs. 40, 94), at the 

 same time rotating the suspensorium backward, or, if the suspensorium is already directed 

 forward, the jaw may be lengthened if its anterior tip grows forward (Figs. 286Z), 289). 

 Similarly a reduction in the size of the mouth (Fig. 286) is very apt to be conditioned by a 

 forward displacement of the quadrate-articular joint. 



