70 William F. Allen 



Each caudal sinus receives a most important communication through 

 its dorso-cephalic wall, which has been described as sinus (x). These 

 sinuses, which follow along the ventro-lateral surfaces of the preceding 

 vertebrae, collect a lateral and a longitudinal haemal trunk, and one or 

 the other of them, the dorsal trunk. 



The dorsal subcutaneous trunk travels along the dorso-median line 

 just below the skin, but when the dorsal fin is reached, instead of 

 dividing into two circular canals at the insertion of the dorsal fin, as 

 in the Selachians and most Teleosts, it passes completely through the 

 basal canal of the fin, and, like the caudal trunk, receives a pair of 

 canals from each ray. These canals drain a network of vessels which 

 is decidedly lymphatic in the character of its meshes, and which, so far 

 as I am aware, has no connection with the arteries. "When about equi- 

 distant from the posterior insertion of the dorsal and the base of the 

 caudal fin it makes a ventral bend to cross the vertebral column, usually 

 the right side, and culminates in the corresponding sinus (x), differing 

 considerably in its termination from Hopkin's description for Amiatus, 

 where it bifurcated, each fork uniting with the lateral trunk, imme- 

 diately before the latter joined the caudal sinus. 



As has been pointed out, the venous supply from the dorsal fin is 

 collected by a pair of dorsal fin ray veins from each ray. In position 

 these veins and the corresponding arteries are nearer the surfaces of 

 the rays than the dorsal fin ray subcutaneous canal. In the basal canal 

 of the fin they unite to form a dorsal fin vein, which passes through the 

 basal canal in company with the dorsal subcutaneous trunk and the 

 dorsal fin artery. Upon leaving this canal the dorsal fin vein in the 

 two specimens in which it Avas traced out crossed the left side of the 

 vertebral column to terminate in the caudal vein. The distribution of 

 this vein recalls the vena postica of Mayer and Parker for the Sela- 

 chians, and had it anastomosed with the dorsal subcutaneous trunk at 

 the posterior border of the dorsal fin we would have had a condition 

 of affairs almost identical with that found in the Selachians. 



With Lepisosteus the lateral subcutaneous trunk offers few peculiari- 

 ties not found in Amiatus or the Teleosts. In the Selachians and in 

 Polyodon they are less sinus-like than in the bony Ganoids and in the 

 Teleosts. In Lepisosteus, as in other fishes, they collect numerous paired 

 transverse or intermuscular l)ranches, which receive a rather coarse 

 network of branches from the connective tissue binding the skin to the 

 m^'otomes. These transverse branches arc undoubtedly prolonged dorsad 



