270 GILBERT C. BOUIiNE. 



occurs ill Anomia epliippium, and was interpreted by 

 Pelseneer (13) as a relic of the pericardium, a mistake which 

 anybody might be excused for falling iuto^ seeing how 

 peculiar are the relations of the kidneys^ venous channels^ 

 and remuants of the pericardium in that genus. 



The Excretory Organs. 



Sassi (16) is the first author who has given a correct and 

 intelligible account of the kidneys in Anomia epliippium. 

 Fig. 4, which is a reconstruction from one of my series of 

 sections, shows that these organs are extremely similar in 

 -Enigma. The chief difference between the two genera 

 consists in the fact that, whereas in Anomia the left 

 kidney forms a complete loop behind the byssus muscle, in 

 -i35nigma the upper and lower limbs are free fi-om one 

 another posteriorly. In the right kidney the upper limb 

 extends much further back along the intestine in Enigma 

 than it does in Anomia. In all other respects I can fully 

 confirm Sassi's observations. In ^Enigma, as in Anomia, 

 the right and left kidney sacs communicate by a wide 

 opening situated below the auricle (fig. 4, ap.). The left 

 renal sac runs forward, dorsad of the byssus muscle, as far 

 as the foot, and then turns sharply back, running just above 

 the attachment of the axis of the left brauchia as far as the 

 visceral ganglion, where it turns upward and opens into the 

 suprabranchial chamber somewhat in front of the right renal 

 aperture. The left reno-pericardial canal is, as in Anomia, 

 situated far forward near the anterior bend of the renal sac 

 [l. oy. in fig. 4), and the left gonaduct opens into the renal 

 sac by a distinct ciliated funnel situated close above and 

 nearly opposite to the left reno-pericardial canal. The right 

 renal sac is roughly crescontic in shape, the concavity of the 

 crescent embracing the adductor muscle. The right reno- 

 pericardial funnel (;•. ?-j). in figs. 4 and 11) is situated imme- 

 diately below the right auricle, and the right gonaduct opens 



