482 University of California Piiblications in Zoology [Vol. 18 



subscapular joins only the brachial vein, and has no relation to the 

 posteardinal sinus {p. c. s.) all of its blood enters the lateral abdominal 

 vein {Lav.) and passes by the large subclavian trunk {s.cl.v.) 

 through the duct of Cuvier {d. c.) to the heart. 



A second vessel in Heptanchus joining the lateral abdominal almost 

 opposite the place of entrance of the brachial vein, should be further 

 described. This I wish to call the coracoid vein {co. v.) since it passes 

 downward along the posterior margin of the coracoid cartilage. It 

 soon leaves the cartilage, however, and passes directly downward 

 toward the midventral line. In this part of its course it runs in the 

 tissue lying at the base of the pericardio-peritoneal septum. At the 

 midventral line it joins a similar vein from the opposite side and is 

 joined by the ventral cutaneous vein. 



From this it is apparent that the condition in Heptanchus differs 

 radically from that in Mustelus as described by Parker. In Heptanchus 

 the lateral abdominal is the main stem receiving blood from all of the 

 lateral vessels associated with the paired fins and their girdles. From 

 the pectoral fin it is joined by the large brachial ; while dorsally from 

 the girdle it receives the subscapular and its tributary, the lateral 

 cutaneous; ventrally from the girdle it receives the coracoid and its 

 tributary, the ventral cutaneous vein. 



An extremely interesting condition is found in Squalus sucklii 

 which completely bridges these two extreme types. In it the sub- 

 scapular (fig. 2, s. sc. V.) is a continuous vein, as in Heptanchus, and 

 as such belongs to the lateral abdominal system ; but dorsally this 

 vessel comes in contact with and may actually have an opening into 

 the posteardinal sinus (p.c.s.), so that the subscapular connects the 

 posteardinal and lateral abdominal (I. a. v.) systems. Since the lateral 

 cutaneous {I.e. v.) joins the subscapular sinus near the union of the 

 latter with the posteardinal, blood from the lateral cutaneous after 

 entering the subscapular might pass dorsally a short distance into the 

 posteardinal sinus, or ventrally into the lateral abdominal vein. In 

 other words: if the subscapular vein in Squalus sucklii were not 

 secondarily connected with the posteardinal sinus, Squalus would be 

 of the heptanchid type ; while on the other hand if that segment of the 

 subscapular, or any part of it, between the entrance of the lateral 

 cutaneous and the brachial were dropped out, the subscapular, with 

 its lateral cutaneous, would be a tributary of the posteardinal, and 

 hence independent of the lateral abdominal system. 



