164 



MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



The other two reiiiil sacs, the i)osterior .saes. lie at the sides of the Ixxly. widely sei)arate(l 

 from each other. A little posterior to the inner sacs, they are eon.siderahly outside them, to close 

 the ventral sides of the sii(>ll muscles. 



The dorsal wall of each sac is formed by the inner wall of the mantle fold, and is that 

 portion of the inner wall of the mantle fold lying between the anterior ri'iial pores and the base 

 of the posterior gill. The posterior and anterior walls of the sac are formed by septa extending 

 backward and downward from tlu' inner wall of the mantle. They unite around the lobular 

 appendages to form a closed sac, from the posterior edge of which a thin ligament extends back- 

 ward and somewhat inward, attached along one edge to the visceral body wall. (Fig. 3»5, L.) The 

 outer end of the sac is narrowed to form a canal which, running in the substance of the mantle 



vc 



RG PO 

 RSA I BVAJ BAA 

 ROA 



TEXT-FRi y -DIACiRAM OF THK RENAL SACS AND NEIGHBORING OliGANS OF NAUTILUS, AS 



VIEWED FROM THE DORSAL SIDE. 



R(t, anterior renal appendage. 



ROA, antericif ivnal i«iie. 



ROP, posterior renal pore. 



RSA, anterior renal sac. 



RSI', posterior renal sac. 



VC, vena cava. 



X, outline of pericanlial divitiion of cceloiu. 



Y, cul de sac of anterior renal sac. 



AU, anricnlar expansion of left anterior branchial vein. 



HA.\, anterior liranchial artery. 



B.\P, posterior branchial artery. 



I?V.\, anterior liranihial vein. 



BVP, posterior liranchial vein. 



H, heart. 



PGA, anterior pericardial appendage. 



PGP, posterior pericardial appendage. 



PO, pericardial pore. 



close to the ventral surface of the shell muscle outside and ventral to the liranchial artery, opens 

 to the exterior through one of the posterior renal pores. (Fig. 3, RP.) The posterior branchial 

 arteries run through th(> posterior walls of the outer renal .sacs. (Text-tig. tt, BAP.) 



Between the inner and outer renal sacs is left a narrow offset of the pericardial cavity 

 extending into the mantle fold. 'V\w auricular enlargements of the anterior branchial veins lie 

 in this spice. Frt)m the outer end of th(> enlarged auricular portion of the vein where it turns 

 ujiward to pass through the inner wall of the mantle fold, a triangular septum .stretched between 

 the outer and inner walls of the mantle fold extends outward to the lateral edge of the pericardial 

 space. By this means a narrow passage is formed lietween the anterior side of the outer renal 

 sac and the septum. This passage, passing along the outer side of the anterior branchial vein, 

 opens to the exterior through the pericardial pore. (Fig. 3, PP.) 



