DESCRIPTION OF PLATE, 26. 665 



(/), thickened portion of membrane, part of the inner fold of 

 the labrum, corresponding with (/) in fig. 2. 



(g), orifice of the oesophagus, with the front part of the supra- 

 oesophageal cavity cut away ; (g 1 ), lower, expanded, or 

 bell-shaped, end of the oesophagus, in its natural condition. 



(i) (k), concavities for the attachment of muscles running to 

 the mandibles. 



(m), cut off edge of membrane forming the side of the mouth, 

 which cut edge can be followed up above the aperture (d'), 

 where the upper basal end of the palpus has been cut off, 

 and so onwards by (g), to the mandible on the opposite 

 side of the mouth. 



Fig. 4, Mouth of Coronula balcenaris, viewed from the outside, 

 in front, with the inner maxilla, mandible, and palpus on 

 the left side of the figure, and nearly the whole labrum, and 

 the greater part of the palpus on the right side, all cut 

 away. The maxilla, mandible, and basal portion of the pal- 

 pus on the right hand, are pulled out of their proper posi- 

 tions ; for the toothed edge of the mandible ought to have 

 stood higher, and nearly in a line between and behind the 

 outer maxillae, and then the basal margin (e") of the lateral 

 portion of the labrum would be raised, and curling round, 

 would stand nearly where the letter b' is now placed. 



(a) («), outer maxilla, upper free lobe ; {a"), lower and inner 

 free lobe ; (a 1 ), supposed second or middle segment ; 

 (a 2 ), supposed third or basal segment; (a /n ), basal arti- 

 culation of mouth, separating it from the ventral surface of 

 the thorax. 



(b), inner maxilla ; (b'), apocleme of do. 



(c), mandible, upper free segment; (c 1 ), second segment; 

 (c 2 ), third and basal segment, but not separated by an ar- 

 ticulation from the labrum. 



(d), palpus ; {d") y membrane uniting the basal end of the 

 palpus, where attached to the labrum, to the side of the 

 mandible. 



(e"), basal margin of the labrum, on one side, displaced and 

 pulled down. 



(n), orifice of the olfactory pouch. 



5, Balanus amaryllis : mandible; upper free segment, seen from 



the side that faces the labrum ; (p), an arched line, where 

 the thickened membrane of the upper free part terminates, 

 and is united by thin membrane to the near side of the 

 palpus; (</), ligamentous bands for the attachment of 

 muscles. 



6, Balanus amaryllis : palpus, on the same scale as the mandible, 



fig. 5, seen from the outside, so that the further or under 

 face is the side which, towards the right hand, is united 

 to the near face of the mandible, fig. 5; (r), long bristles, 

 springing from a protuberance near the extremity; these 

 bristles, in many species, form a long single row, parallel 



