Subcutaneous Vessels in Tail of Lepisosteus 53 



to run along the septum between two myotomes to the great lateral 

 subcutaneous trunk. Mesad of this canal they break up into numerous 

 branches, which' for the most part follow, superficially, dorsad, or 

 ventrad, along the septa between the myotomes, to form a network in 

 the connective tissue that binds the skin to the body muscles. 



One of the largest of the neural veins is the last one (Figs. 1, 3 and 

 14, Neu. V. (1)). It takes its origin in the posterior dorsal corner of 

 the caudal peduncle. After passing obliquely cephalad for a short 

 distance, it curves ventrad to cross the left surface of the eighth 

 vertebra from the last. It then crosses the left sinus (x) and finally 

 empties dorsally into the caudal vein a little anterior to the openings 

 of the caudal sinuses. In Fig. 5 the abbreviation Neu V. (i) 0. marks 

 the opening of this vein into the caudal. In the first dissections this 

 vein was taken to be a part of the subcutaneous system opening into 

 sinus (x). 



Vascular Supply for the Dorsal Fin. — In the region of the posterior 

 part of the dorsal fin two of the neural vessels are greatly enlarged to 

 supply the dorsal fin. In the specimen from which Fig. 9 was drawn 

 the dorsal fin artery (D. F. A.) took its origin from the caudal artery 

 at about the level of the third vertebra from the posterior end of the 

 dorsal fin. After crossing the right side of this vertebra it crossed the 

 two preceding interneural spines obliquely to enter the basal canal of 

 the dorsal near the middle part of the fin. Here it separated inta 

 three branches; two of which supplied the anterior part of the fin 

 and the third the posterior part. From these branches one or twa 

 dorsal ray arteries (Fig. 9, D. E. A.) were given off to pass along 

 either the anterior or posterior surfaces of the ray or both. In this 

 specimen a second neural or a minor dorsal fin artery supplied the 

 posterior part of the fin (see Fig. 9). With another specimen of 

 L. tristcechus, where the dorsal fin artery was dissected out, it had its 

 source about nine vertebrse cephalad of its position in Fig. 9, and 

 approached the dorsal fin from in front. The dorsal fin vein (Fig. 9, 

 D. F. V.) emptied into the caudal vein two vertebrge behind the origin 

 of the dorsal fin artery. Tracing this vein peripherally, it was seen to 

 cross the left side of the second vertebra, behind the dorsal fin artery. 

 Continuing dorsally behind its neural and interneural spines it entered 

 the basal canal of the dorsal spine from the rear, and traveling clear 

 through this canal it was supplied from numerous dorsal fin ray veins 

 (Fig. 9, D. R. v.), which may traverse either the anterior or posterior 



