BEACHIOPODA. 



369 



wltii con'csponding ribs ; hinge-line wide and straight, with a 

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

 mentary ; interior of dorsal valve with one or more j)rominent, 

 sub-marginal sej)ta ; loop two or four-lobed, adhering to the 

 septa, and more or less confluent with the valve 



Fig. 162. A. decollata, ^ ; dorsal vaire 'with the animal, from a specimen dredged 

 l)y Professor Forbes in the iEgean. Tlie oral aperture is seen in the centre of the 

 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. 



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

 Mediterranean. 30 — 105 fathoms. 



Fossil, 19 species. Oolite — . Europe. 



Fig. 163. T. radians. Fig. 164. T. Mediterraneum.* * 



Tkecidium, Defrance. 

 Etymology, Thelcidion, a small pouch. 

 Type, T. radians, PI. XT., Fig. 11. 

 Shell small, thick, punctate, attached "by the beak ; hinge* 



« Dorsal valve with the animal, magniSed, Coll. Davidson. 



e3 



