GREGORY: FISH SKULLS 



225 



general appearance. On the whole, the skull type suggests rather those of the Umbridae 

 and PoeciliidsE. 



In Gasterosteus spinachia (No. 87, Brit. Mus. Nat. Hist.) the preorbital face is decidedly 

 longer. The premaxillae have long ascending processes, indicating marked protrusility. 

 The opercular region and the skull top suggest the poeciliid type. 



Gasterosteus spinachia 



Fig. 103. Gasterosteus spinachia. 



The elongation of the preorbital face is carried to an extreme in Aulostomus (Fig. 104) 

 and still more in Fistularia (Fig. 105). We have already seen several types of fishes in 

 different orders in which the suspensorium was inordinately produced forward, but nothing 

 approaching the condition in Fistularia is known outside its own group. Much the greater 

 part of the long tube that lies between the mandible and the eye is roofed by the meseth- 

 moid, the remaining part being contributed by the vomer. Beneath this lies the elongated 





j>ta 



pun 



Aulostomus maculatus 



Fig. 104. Aulostomus maculatus. After Jungersen. 



entopterygoid, quadrate, interopercular and preopercular. In the top view the small 

 supraoccipital is seen to be wedged in between the appressed epiotics. No parietals are 

 present. Doubtless in order to strengthen the vertebral column against the adverse lever- 

 age of the excessively long skull, the four anterior vertebrae are greatly elongated, with 

 wide parapophyses, the whole complex being fused into a rigid tube. In Aulostomus the 

 specialization of the skull is less advanced than that of Fistularia. In the Syngnathidae 

 (pipe-fishes and sea-horses) the skull (Fig. 106) is fundamentally the same as in Fistularia 

 but even more specialized. 



The skull of Phyllopteryx (Fig. 106), as figured by Jungersen (1910, Pi. V, Fig. 8) has 



