THE CLUPEOID CRANIUM AND THE SWIMBLADDER 445 



ing to be untenable. For example, he describes a utricular 

 diverticulum in the anterior bony capsule, the existence of 

 which no investigator since Weber has accepted; he describes a 

 caecum of the utriculus ('bulbe accessoire' of Breschet), al- 

 though Hasse had stated that this structure is not connected 

 with the membranous labyrinth; he revives Weber's conception 

 of the subcerebral canal, although no investigator since Weber 

 has admitted it to be an endolymphatic connection. 



In papers on the osteology of the skull in various lower groups 

 of Teleosts, Ridewood ('04 a, b,) describes the form and rela- 

 tions of the bony capsules of the swimbladder in several genera 

 of Clupeidae and related families. Essentially the same rela- 

 tions are found not only in all species of Clupeoids, but also in 

 Chatoesus, Chirocentius, Dussumieria, Engraulis, Coila, Pellona, 

 Pellonula, Pristingaster, and Hyperlophus. The posterior cap- 

 sule is wanting in Clupea sprattus, and both anterior and posterior 

 capsules are absent in Chanos salmoneus. In Coilia nasus there is 

 also a large exoccipital capsule corresponding, in Clupea, to the 

 fusiform enlargement of the exoccipital part of the bony tube. 

 Megalops has a structure in the opisthotic bone which perhaps 

 lodges a swimbladder vesicle. Ridewood also states that ves- 

 icles occur in the skull of Hyodon, Notopterus, and in the 

 Morymoids. 



The structure of the skull and its relations to the swimbladder 

 in these last three genera are more fully described by Ridewood 

 (04 c) and by Bridge ('00). The ear-swimbladder relation in 

 these forms is unlike that of Clupeoids; it belongs with the first 

 or primitive type as described above. 



All the writers above discussed are to be classed together so 

 far as their method, technique, and results are concerned. They 

 relied entirely on dissection and injection methods and made 

 little or no attempt to investigate minute relations. The next 

 two writers, however, applied more modern and accurate 

 methods. 



Tysowski ('09) shows that both the subcerebral and supra- 

 cerebral connections between the membranous labyrinths of the 

 two sides are not endolymph tubes, but channels in the tissue 



