396 NOTES AND MEMX)RANDA. 



ciliated on its margin, and nninterruptedly continued round 

 the anal side of the opening, but deficient on the opposite 

 side. The interior of the lobe is occupied by a cavity. 



A large part of the mantle cavity is occupied by the 

 pharynx, a spacious thin-walled sac which opens into the 

 mantle cavity by a long curved slit with thickened and 

 ciliated margins, which, at the ab-anal side, are continued 

 beyond the opening in the base in the form of two short 

 ciliated tentacles. Towards the apex the pharynx becomes 

 suddenly narrow, and is here lined by vibratile cilia, and 

 marked by circular strise, which possibly indicate the presence 

 of sphincter-like fibres. It now turns towards the anal side, 

 and then bends downwards towards the base, and enters a 

 thick-walled sub-cylindrical stomach. This runs towards the 

 base parallel to and a little within the anal edge of the test, 

 and is ultimately continued into a short straight intestiiie, 

 which terminates by an anal orifice on the mantle cavity near 

 the outer opening of the latter. From the upper part of the 

 walls of the pharynx a narrow bundle of fibres passes to the 

 apex of the mantle cavity. 



Upon each side of the pharynx and lying against the 

 stomach and intestine is a large oval mass. Its situation 

 would suggest the probability of its being an hepatic organ, 

 but it is altogether so enigmatical that it would be rash to 

 insist on assigning to it any special significance. 



In contact with each of these enigmatical organs is a 

 small tubercle, from which a bundle of short fibres pass off" in 

 a radiating direction. The resemblance of these bodies to a 

 pair of nervous ganglia is obvious, but the author was more 

 inclined to regard them with Schneider as indicating points of 

 attachment of the contained animal to the two valves of the test. 



The smaller of the tAvo openings in the base, that, namely, 

 which is situated near the ab-anal edge of the animal, is, 

 like the other, surrounded by a hollow membranous lobe 

 with ciliated margin. This is uninterruptedly continued 

 round the ab-anal side of the opening, but is deficient on 

 the opposite side. The opening leads into a special chamber, 

 entirely shut off from the cavity of the mantle and from the 

 pharynx. The walls of the chamber are lined Avith cilia, 

 and it has within it, or in immediate connection with its 

 walls, tAvo peculiar structures. One of these is a somewhat 

 pyriform organ, which, with one end close to the orifice of the 

 chamber, extends from this point into its cavity ; it is com- 

 posed of a mass o'f spherical bodies. The other extends 

 over the roof of the chamber in form of a cap : it consists of 

 two portions, one of which lies directly on the walls of the 



