A Cirriped Crustacean. 101 



A CIRRIPED CRUSTACEAN 



(Lepas fascicitlaris). 



External Anatomy. The highly specialized animal is 

 attached at its anterior end by an elongated peduncle, and is 

 protected laterally by a mussel-like shell. Of how many 

 pieces does the shell consist? Do you find an elongated 

 opening between the two halves of the shell? The opening 

 is on the ventral side. The median, dorsal piece of the 

 shell is the carina, while lying laterally are the more pos- 

 terior terga and the more anterior and ventral scuta. The 

 scuta join in the mid-ventral line. From the ventral open- 

 ing the six pairs of biramous appendages are thrust out for 

 the securing of food. 



Draw the animal as seen from the right side, naming the 

 parts. 



Stretch apart the valves and note that the integument of 

 the animal, externally indurated with lime, passes, within 

 the ventral opening, into a more delicate transparent fold, 

 which completely separates the soft parts of the animal 

 from the exterior. Note in particular the deeply lying 

 oral cone, 1 the attachments of the biramous appendages, 

 the aborted abdomen, and the greatly elongated intro- 

 mittent organ, which occupies a position just back of 



1 The oral cone is a large knob-like mass which is made up of the 

 mouth-parts, and bears, at its apex, the mouth. 



