Subcutaneous Tessels in Tail of Lepisosteus 6',) 



venous opening is guarded b}' a pair of semi-lunar rahrs (Figs. 4, 5 

 and 7, E. and L. Cau. S. V.), which open into the vein. 



That part of the caudal vein which receives the caudal sinuses is 

 enlarged almost into a reservoir, which in addition receives the last 

 neural vein and the posterior part of the caudal vein from the tail. 



With Lepisosteus the term caudal sinus is nothing more than an 

 arbitrar}^ term applied to two non-contractile reservoirs situated ventrad 

 of the last vertebrge, near the base of the tail, which collect four longi- 

 tudinal subcutaneous trunks, together with two longitudinal haemal 

 trunks, and empty into the caudal vein. 



Summary and General Considerations. 



In the tail region of Lepisosteus there are four longitudinal sub- 

 cutaneous vessels and two profundus trunks in the haemal canal, which 

 collect a subcutaneous network that so far as could be determined is 

 entirely separated from the arteries or their capillaries, and which in 

 one way or another terminate in two caudal sinuses that discharge them- 

 selves in the caudal vein. 



The two caudal sinuses are elongated reservoirs situated ventrad of 

 the posterior end of the vertebral column. They communicate mesad 

 with each other, dorso-cephalad with what has been designated as sinus 

 (x), and ventro-cephalad with the caudal vein, the latter orifice being 

 guarded by a pair of semi-lunar valves. 



Posteriorly one of the caudal sinuses, more often the right, receives 

 what has been described as the caudal trunk, which is merely a prolonga- 

 tion of the ventral trunk passing through the basal canal of the caudal 

 fin, where it runs parallel to a corresponding caudal artery and vein. 

 From each ray. it receives two branches which traverse the dorsal and 

 ventral surfaces of the ray and collect a rather coarse network of vessels 

 from the fin membrane. This network is not continuous with arterials 

 from the fin ray arteries. The caudal trunk in its course from the tail 

 to the caudal sinus follows the caudal artery, and is in fact a deeper 

 lying trunk than the caudal vein, which passes cephalad between the 

 superficial and profundus muscles of the caudal fin. 



The ventral trunk, of which the caudal is a posterior continuation, 

 travels along the ventro-median line, just Avithin the skin. In passing 

 through the basal canal of the anal fin it collects paired branches from 

 each ray, which receive a network from the fin membrane similar to 

 that found in the caudal fin. 



