TRIOPA. 



The ganglia of the nervous system resemble those of JEgirus. There are two pairs of 

 oesophageal centres, the median and upper one being composed of two large oblong masses,, 

 placed close together, and united above the alimentary tube. These mases are formed by the 

 fusion of the cerebroid and branchial ganglia. They distribute their nerves almost exactly as 

 in JEgirm, and the olfactory nerves have at their origin each a considerable ganglionic 

 enlargement. The pedial ganglia rest against the sides of the oesophagus, and are united 

 below that tube by a short commissural cord, — the great oesophageal collar : they give three 

 nerves to the foot. A visceral nerve comes off from a small ganglion, closely attached to the 

 branchial portion of the right central mass. 



The buccal ganglia are in close contact with each other ; and are united to the upper or 

 central masses by shorter cords than usual. 



The eyes, which are of the usual character, receive their nerves from minute elliptical 

 ganglia^ attached to the external margins of the cerebroid portion of the central masses. The 

 auditory capsules are situated at the junction of the same masses with the pedial ganglia, and 

 appear to belong to the cerebroid portion of the former. They contain numerous elliptical 

 otolithes. 



The skin is much stiffened and crowded with spicula, which are large, strong, and 

 generally bifurcated at one end. 



