216 



MANUAL OF THE MOLLUSCA. 



Snh-genera. Terehratullna (caput-serpentis) D'Orb. PI. XV. fig. 3. 

 Fig. 112. Shell finely striated, auriculate, deltidium usually rudiraental ; 



Dorsal valve: 



Animal. ^■ 



foramen incomplete ; loop short, rendered annular in the adult by the union 

 of the oral processes. Dist. 7 sp. IT. States, Norway, Cape, Japan. 10— 

 1 20 fms. Fossil, 20 sp. Oxfordian — . U. S. Europe. 



Waldheimia (australis) King. PI. XV. fig. 4 (p. 8, figs. 4, 5.) figs. 109, 

 118, 114. 



Fig. 113. Dorsal valve. 



Fig. 114. Ventral valve. 



Fig. 113. j, cardinal process; t', dental sockets; p, hinge-plate; s, septum; c, 

 crura of the loop ; I, reflected portion of the loop : m, quadruple adductor-impression. 



Fig. 114./, fc-amen; d, deltidium; t, teeth; a; single adductor-impression; r, 

 cardinal muscles ; x, accessory muscles ; p, pedicle muscles; v, position of the vent ; 

 z, attachment of "pedicle-sheath. 



Shell smooth or plaited, dorsal valve frequently impressed ; foramen com- 

 plete ; loop elongated and reflected ; septum {s) of smaller valve elongated. 

 Distr. 9 sp. Norway, Java, Australia, California, Cape Horn. Low-water — 

 100 fms. Fossil, 60 sp. Trias — . S. America, Europe. Euclesia fcar- 

 dium) King, includes 1 recent, and 6 fossil species which are sharply plaited, 

 T. impressa (PI. XV. fig. 5) is the type of a group which has the external 

 shape of Terehratella. 



