similar development of longitudinal rows of valves in the conus. In _Amia_ (fig. 26, B), however, the conus is shortened and the number of valves in each longitudinal row is much reduced. This leads to the condition found in the Teleosts (fig. 26, O), where practically all trace of the conus has disappeared, a single circle of valves representing a last survivor of each row (save in a few exceptional cases, e.g. _Albula_, _Tarpen_, _Osteoglossum_, where two valves of each row are present). [Illustration: After Newton Parker, from _Trans. of the Royal Irish Academy_, vol. xxx. FIG. 27.--Venous System of _Protopterus_, as seen from ventral side. a, Atrium. k, Kidney. ac, Anterior cardinal. l, Liver. an.v, Anastomotic vein. ov.v, Ovarian veins. c, Intestine. p, Pericardium. c.v, Caudal vein. p.c.v, Left posterior cardinal. f.v, Femoral vein. p.v´, Parietal veins. g.b, Gall-bladder. r.p.v, Renal portal. h.v, Hepatic vein. s, Stomach. i.j.v, Inferior jugular vein. s.b.v, Subclavian.] i.v.c, Posterior vena cava. In Front of the conus vestige of the Teleost there is present a thick walled _bulbus aortae_ differing from the conus in not being rhythmically contractile, its walls being on the contrary richly provided with elastic tissue. The Dipnoans[37] show an important advance on the conus as in atrium and ventricle. The conus has a characteristic spiral twist. Within it in _Neoceratodus_ are a number of longitudinal rows of pocket valves. One of these rows is marked out by the very large size of its valves and by the fact that they are not distinct from one another but even in the adult form a continuous, spirally-running, longitudinal fold. This ridge projecting into the lumen of the conus divides it incompletely into two channels, the one beginning (i.e. at its hinder end) on the _left_ side and ending in front _ventrally_, the other beginning on the _right_ and ending _dorsally_. In _Protopterus_ a similar condition occurs, only in the front end of the conus a second spiral fold is present opposite the first and, meeting this, completes the division of the conus cavity into two separate parts. The rows of pocket valves which do not enter into the formation of the spiral folds are here greatly reduced.