18 G. O. Sars. 



apical one is fully twice as long as the other, though not 

 attaining half the length of the ramus. Both claws are 

 but very slightly curved, and are finely denticulated along 

 their concave edge. Just in front of the apical claw issues 

 from the tip of the ramus a rather long bristle curving 

 downwards in front of the latter, and another much smaller 

 one is seen attached to the dorsal edge, immediately above 

 the other claw. 



Inner organs. 



In order to examine the inner organs in their natural 

 situatiou, it may be convenient to detach the animal 

 carefully from its shell, and to place it for some time 

 in absolute alcohol, then either transferring it to oil of 

 cloves at once, or after having previously stained it very 

 slightly with hæmatoxylin or carmine. The animal may 

 then be mounted in canada balsam either entire or in 

 parts. Some of the inner organs, especially those contained 

 within the lamellæ of the valves, may however be equally 

 well examined in quite fresh specimens. 



The intestinal canal commences with a muscular oesophagus 

 ascending perpendicularly from the oral aperture, and join- 

 ing the intestine proper by a somewhat tumefied part 

 strengthened, according to Zencker, by several chitinous 

 lamellæ. The intestine proper (see pi. 1, fig. 3) is very 

 capacious, occupying a great part of the inner cavity of 

 the body. It is divided into two very sharply defined 

 parts, one anterior, the stomach, and one posterior, the gut 

 these being separated by a strong constriction occurring about 

 in the centre of the body. The stomachal portion is pro- 

 duced above to a large rounded sac advancing over the 

 anterior part of the gut, and sends off from each side, 



