( 35 ) 



DIVISION XXIII. SESSILES. 



Operculum interior, 

 4-valved, valves move- 

 able, inserted near the 

 internal base of the 

 shell. (1) 



Operculum of 4 ob- 

 tuse valves. (2) 



(3) 



Operculum of 4 valves. 



GENERA. 



6. Balanus. Lam. M. 



Fixed, conical, trnn- 

 cated at summit, closed at 

 the bottom by a testaceous 

 adhering plate, open at 

 the top, sub-trigonal or 

 elliptic. Fig. 107, 110. 



7. Coronula. Lam. M. 



Yalves altogether ap- 

 pearing sub - orbicular, 

 coniform, truncated at the 

 extremities ; divisions or 

 partitions very thick, hol- 

 lowed by radiating cells. 

 Fig. Ill, 112. 



8. Acasta. Leach. M. 



Sub - conical ; cone 

 formed of six lateral une- 

 qual valves, having an 

 orbicular plate at the bot- 

 tom, concave internally, 

 resembling a goblet or 

 patella. Fig. 116. 



9. Creusia. Leach. M. 



A convex cone, com- 

 posed of four unequal 

 valves, distinct by the 

 sutresu. Fig. 114. 



10. Tubicinella, Leach. 



M. 



Valves forming a tubu- 

 lous straight shell, attenua- 

 ted towards the base, 

 truncated at both ends, 

 open at the top, and the 

 base closed by a mem- 

 brane, furnished with 

 transverse callous pads. 

 Fig. 115. 



(1) They abound in almost all seas, and attach themselves to all sorts of sub- 

 stances. They are found in a fossil state in Italy, and in England in Crag Marl. 



(2) They live in the bodies of marine animals, and have even been found, with 

 the Tubicinella, within the fat of whales ; they also adhere to shells. 



(3) They are found in sponges, and never fix on hard or solid bodies. 



(4) These and the Pyrgomaz are generally affixed to Madrepores : the Creusiat 

 are from the Northern and Indian Seas. 



(5) There is but one species known, found on the South American whale?, 



C 



Operculum interior, 

 bivafved. (4) 



Operculum of 4 ob- 

 tuse valves. (5) 



