On the process of disappearance of the conus arteriosus in Teleosts

Considerable difficulty has been encountered in the classification of fishes and their different genera, and especially in drawing a distinct line between the Ganoids and Teleosts.Gegenbaur ('66) found in the Ganoids and in a limited number of Teleosts, intercalated between the ventricle of the heart and the truncus arteriosus, two segments clearly distinguishable from one another.Of these segments, the caudal is called the conus arteriosus or bulbus cordis, while the cranial is called the hulbus arteriosus.The conus arteriosus is a well-marked muscular structure.furnished with numerous valves, and is one of the characteristics of the Elasmobranchs and Ganoids.Teleosts, with the cxception of a very limited number, have no conus.It was once thought that the rudimentary conus, or its total absence, with but one tier of valves, was characteristic of the