DEEP-SEA PROTOBRANCHIA (BIVALVIA) 



robust shells with lunule & escutcheon 

 long broad continuous hinge 

 large adductors 



P.minuta 



Rfora 



P. lenticula 



R abyssorum 



87 



hind gut thru' 

 to left 



Y.curta- 



Y.veletta 



\ ? 



short hinges 



v . /. 



Y.inconspicua 



Y.extensa 



Y.argentinea 



fragile shells without lunule & escutcheon 

 separate hinge plates 

 moderately large subequal adductors 



Y.fabula 



subrostrate 

 long hinges 

 small unequal adductors 



V shaped hind guts 



Y.artipica 



^-'? 



Y.bilanta 



Y.hanna 



Y.capensis 



Y.sinuosa 



Y.blanda 



Y.biscayensis 



Y.pseudo 



Y.enata coils 

 Y.jeffreysi 



I 

 Y.ella 



Y.lucida 

 Y.obesa 

 Y.similiris 



single 

 hind gut loop 



Y. perplex a 



ata Y.similis 



ovate 



loops 



Y.americana 

 Y.subcircularis 

 Y. biguttata 

 Y. ovata 



I 



Y.insculpta 



multiple 

 hind gut loops 

 & coils 



increasing 

 shell height 

 &hind gut length 



ig. 148 Diagram to show resemblances in shell form of the deep-sea species of the genus Yoldiella found in the Atlantic, arranged in 

 increasing length and complexity of the hindgut and each group of species arranged in increasing depth sequence. 



