BEACmoPODA. 



369 



■witli Corresponding ribs ; hinge -line wide and straiglitj witli a 

 narrow area to each valve ; foramen large, deltidium rudi- 

 mentary ; interior of dorsal valve with one or more prominent, 

 sub-marginal septa ; loop two or four-lobed, adhering to the 

 septa) and more or less confluent with the valve 



Vig, 162. A. decollata, ^ ; dorsal valve with the animal, from a specimen dredged 

 h)' Professor Forbes in the ^gean. The oral aperture is seen in the centre of tlie 

 disk. 



Animal with oral arms, folded into two or four lobes, united 

 by membrane, forming a brachial disk fringed with long cirri; 

 mantle extending to the margins of the valves, closely adherent. 



Distribution, 5 species. North Britain, Madeira, Canaries, 

 Mediterranean. 30— lOo fathoms. 



Fossil, 19 species. Oolite — . Europe. 



Tig. 163. Jl radians. Fig. 164. T. Mediterfaneum,* *■ 



ThecIDITJM, Defrance. 

 Etymology, Tliekidion, a small pouch. 

 Type, T. radians, PL XV., Fig. 11. 

 Shell small, thickj punctate, attached by the beak ; hin^e- 



* Dorsal valve vpith the anitoal, magnified. Coll. Davidson. 

 R o 



