Subcutaneous A'essels in Tail of Lepisosteus. 55 



The distribution of the blood vessels to and from the anal fin was 

 not studied. One, however, would naturally expect to find it supplied 

 by an enlarged hsmal artery and vein, somewhat after the general plan 

 of the dorsal fin. 



SUBCUTAXEOUS YeSSELS OF THE CaUDAL FiX. 



As with most fishes four longitudinal subcutaneous trunks, respect- 

 ively, dorsal, lateral and ventral, are to be found immediately below 

 the skin in Lepisosteus. In one way or another they discharge them- 

 selves posteriorly into two caudal sinuses, which empty into the caudal 

 vein. 



Ventral Subcutaneous Trunh (Figs. 1, 2, 3, 5 and 10-16, V. T.). — 

 This important canal travels along the ventral median line, directly 

 under the skin, in a mass of connective tissue that binds the two great 

 lateral muscles. As stated in a previous paper {cp. cit., p. 114), this 

 canal usually bifurcates anteriorly, each fork terminating in its respec- 

 tive pericardial sinus. Upon tracing this canal caudad it was found to 

 enter the basal canal of the anal fin, and to receive an anal fin ray canal 

 (Figs. 1 and 2, A. E. C.) from the anterior and posterior surfaces of 

 each ray, which drains a network of canals from the membrane con- 

 necting each two rays. After leaving the anal fin, this trunk continues 

 along the ventral surface of the caudal peduncle, to penetrate the basal 

 canal of the caudal fin, and to become the caudal subcutaneous trunlc 

 (Figs. 1-5, 7, 17-19, C. T.). It receives here, as within the anal,canal, 

 two caudal fin ray canals (Figs. 1, 2, 18 and 19, C. E. C), which run 

 along the dorsal and ventral surfaces of each ray, and receive a network 

 of canals from the membrane joining two rays Upon reaching the 

 third or fourth ra}' (counting dorso-ventrad) the caudal trunk makes 

 a sharp curve at right angles to pass cephalad along the upper margin 

 of the ninth or tenth of the last haamal spines (counting ventro- 

 dorsad), in company with, but below, the caudal artery, to empty into 

 either the right or the left caudal sinus; oftener into the right. 



Fig. 18 shows the caudal trunk of a 90 mm. Lepisosteus osseus, twice, 

 in cross section. Toward the lower j^art of the figure it is seen traveling 

 along through the basal canal of the caudal fin, and 1)elow the vertebral 

 column it is seen again not far from its entrance into the right caudal 

 sinus. In Fig. 23 we have a view of the posterior part of the caudal 

 trunk higfhlv magnified. It consists solelv of a laver of endothelium 



