BLOOD- VASCULAR SYSTEM OF THE LORICATI II3 



All species of Scbastodcs examined had a distinct renal por- 

 tal system, which in the main resembled Ofhiodon; however, 

 the renal portal veins extend much further cephalad, there is 

 always one or more posterior air-bladder veins emptying into 

 the renal portal system, and there is no posterior mesenteric 

 vein. The kidne}^ itself differs considerably in shape from that 

 of the other genera ; while it usually occupies a large portion 

 of the dorsal part of the short thoracic cavity, still a large por- 

 tion of the organ is crowded cephalad into the two forks. The 

 caudal vein (PL IV, fig. 31 ; Cau.V.) after piercing the pos- 

 terior dorsal side of the kidney continues cephalad along the 

 dorsal surface of the kidney for some little distance as a renal 

 ^07-tal vein and not until the kidney forks does this vein sepa- 

 rate into the renal portal veins (fig. 31, Ren.P.V.). These 

 veins continue cephalad in their respective lobes until near the 

 point of union of the cardinals with the jugulars, giving off 

 numerous afferent renal veins, and the renal portal itself re- 

 ceives the following vessels. First, the spermatic vein (fig. 31 ; 

 Sper.V.), which is formed from the posterior union of the right 

 and left spermatic veins. In its dorsal course about midway 

 between the reproductive organs and the kidney it receives the 

 urinary bladder vein (fig. 31 ; Ur.Bl.V.), and immediately be- 

 fore emptying into the renal portal, a small suprarenal vein. 

 Shortly after receiving the spermatic, the caudal or renal por- 

 tal receives a rather large posterior air-bladder vein (fig. 31 ; 

 P.A.Bl.V.), which arises from a regular network of vessels on 

 the posterior end of the air-bladder. In the specimen from 

 which fig. 31 was drawn, two smaller posterior air-bladder 

 veins were also noticed ; one of which terminated in the renal 

 portal vein, and the other in the right cardinal. Usually, how- 

 ever, there is but one posterior air-bladder vein, and it may 

 empty into either the right cardinal or the renal portal vein. 

 The right cardinal is almost identical to the similar vessel of 

 the other genera, and a description of it is unnecessary. 



VIII. VASCULAR SYSTEM IN AXOPLOPOMA. 



Three specimens of this species were brought in by Chinese 

 fishermen when this paper was about finished. All were in- 



Proc. Wash. Acad. Sci., June, 1905. 



