EXPLANATION OF THE PLATES. 389 



4. Lithotrya Rhodiopus, (magnified five times,) internal 



views of; («), scutum; {5), 

 tergum ; (c), latus ; id), 

 carina. 



5. Lithotrya Valentiana, (magnified between three and 



four times ;) (a), internal 

 view of scutum and tergum, 

 locked together ; {5), capi- 

 tulum seen from vertically 

 above ; (c), internal view of 

 carina; {d), section across 

 the middle of the carina. 



TAB. IX. 



1. Lithotrya truncata, (magnified four times.) 



Id. „ „ capitulum seen from vertically 



above, not so distinctly repre- 

 sented as in fig. hb, PL VIII. 



16'. „ „ internal views of valves; (a), 



rostrum, with a few subjacent 

 scales of the peduncle ; {5) f 

 scutum ; (c), tergum ; (d), 

 carina. 



2. A portion (about ^th of an inch square) of the sur- 



face of attachment of the peduncle of Pollicipes 

 polymerus, seen from the outside, greatly magni- 

 fied, showing the small circular {55) patches of 

 cement, poured out from the cement-ducts {ad) 

 which lie within the peduncle. 



2d. „ „ a section, still more magnified, 



through the basal membrane 

 of the peduncle, through one 

 of the loops of the cement- 

 ducts {ad), and through one 

 of the circular patches {5) of 

 cement. 



