DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS II 5 



in Scorpce)u'cht/iYS and Aiiiia. In Lcpisostcus it follows along 

 the front and inner surface of the pectoral arch parallel with the 

 precava. Dorsad at about the level of the last branchial arch it 

 communicates with what is designated as the occipital sinus 

 (Figs. 8-12, Oc.S.), which continues ventrad, mesad of the 

 pericardial sinus, and shortly after receiving the pectoral sinus 

 (Figs. 8 and 9, I^.S.), it again joins the pericardial sinus from 

 the inside through a very large orifice (Figs. 8-10, Oc.S.O.). 

 As already stated, in the region of the heart one or both of the 

 pericardial sinuses receive the ventral lymphatic trunk or a fork 

 of it. After which the pericardial sinus proceeds along the lat- 

 eral surface of the ventricle, just outside the parietal layer of 

 the pericardium, and when the bulbus arteriosus is reached each 

 of the pericardial sinuses has a very large opening (Figs. 8, 9, 

 13, 14 and 15, Per.S.O.), which leads into a large canal that 

 passes mesad and empties into the posterior end of the so- 

 called dorsal pericardial sinus. This sinus (Figs. 13 and 15, 

 D.Per.S.), which is located directly above the bulbus arteri- 

 osus, has the form of an ellipse with its longest axis corre- 

 sponding with that of the fish. In a lo-pound L. osseus its di- 

 mensions were 15 by 8 mm. There is always a communication 

 above with the inferior jugular vein. In the specimen from 

 which Fig. 15 was drawn there were two such openings, both 

 of which were located in the posterior half of the sinus, and 

 were guarded by a pair of semi-lunar valves {D.Per.S. V.) 

 opening into the vein. In this specimen there was a third 

 aperture in the anterior dorsal wall of this sinus, but it led only 

 into a small blind pocket. This mechanism in Lepisosteus re- 

 calls a sort of hypothetical connection of the ventral pericardial 

 sinus with a branch of the inferior jugular in Scorpmnichthys 

 {op. cit., p. 75). At the points where the connecting branches 

 are given off from the pericardial sinuses to the dorsal peri- 

 cardial sinus two anterior pericardial canals are received (Figs. 

 13, 14 and 15, Per.S.{i)). These doubtless are nothing more 

 than the anterior continuations of the pericardial sinuses, which 

 extend for a short distance along the ventral surface of the 

 parietal layer of the pericardium. 



Occipital Sinus (Figs. 8-12, Oc.S.). — As will be readily 



