Subcutaneous Vessels in Tail of Lepisosteus 57 



circular trunks about its base as in most fishes, it passes entirely through 

 its basal canal, and receives two dorsal fin I'ay canals (Figs. 1 and 2, 

 D. E. C), which traverse the anterior and posterior surfaces of each ray 

 to receive a network of vessels from the fin membrane. In position 

 the fin ray canals are more distal from the rays than the corresponding 

 arteries and veins. Unlike the ventral trunk, the dorsal does not 

 extend to the tail, but about midway between the posterior end of the 

 dorsal fin and the beginning of the caudal it makes a sharp bend at 

 right angles to continue ventrad across either the right or the left side 

 of about the eleventh vertebra from the last, and here culminates in a 

 longitudinal sinus, designated as sinus (x). With both L. tristcechus 

 and L. osseus the dorsal trunk may empty into either the right or the 

 left sinus (x), but in no specimen did the dorsal trunk bifurcate and 

 each fork terminate in a sinus (x). In the specimens from which 

 Figs. 2 and 5 were drawn the dorsal trunk crossed the right side of the 

 vertebral column and ended in the right sinus (x) ; while in the speci- 

 men from which Fig. 3 was drawn it crossed the opposite or left side 

 of the vertebral column and emptied into the left sinus (x). Fig. 12 

 shows the dorsal trunk of a 90 mm. L. osseus, in section, passing across 

 the left side of the vertebral column, and Fig. 13 its termination in 

 the left sinus (x). 



Sinu^ (x) (Figs 1-6 and 11-16, x). — The two sinuses so designated 

 are situated deeply along the lower and outer surface of the vertebral 

 column, somewhere between the sixth and the thirteenth from the la?t 

 vertebra. They are variable in length, position and in their mode of 

 connections; both in different specimens and on the opposite sides of 

 the same individual. Both of these sinuses receive a lateral sub- 

 cutaneous trunk and a haemal longitudinal trunk, communicate ventrad 

 with a caudal sinus that empties into the cardinal vein, and one or the 

 other of them receives the dorsal subcutaneous trunk. In Figs. 1, 3, 

 4, 5 and 6 the anterior end of sinus (x) received the lateral trunk from 

 the side and the haemal trunk from below and within; while in Fig. 2, 

 which is the opposite side of the same individual as Fig. 1, the lateral 

 trunk joined this sinus considerably caudad of the union of the dorsal 

 trunk; in fact, the opening was about opposite the connection of sinus 

 (x) with the caudal sinus. In the dissection of L. tristcechus from 

 which Figs. 1 and 2, and the dissection of L. osseus from which Figs. 

 5 and 6 were drawn, the dorsal trunk terminated in the right sinus (x), 

 about midway between the anterior and posterior extremities; while 



