60 ADKATE. 



ADDUCTOE MUSCLE. That which draws the two valves of a 

 shell together, and leaves a mark on the inner surface of each, 

 called the Muscular Impression. 



ADELOSINA. D'Orb. A genus of microscopic Eoraminif era. 



ADEOE.BIS. "Wood. A genus of Trochseform sheUs, approach- 

 ing Delphinula, and represented by Ad. subcarinata. PI. xxviii. 

 f. 588. 



ADESMACEA. Bl. {a, without ; Aec^a, desma, ligament.) The 

 10th family of the order Lamellibranchiata, Bl. composed of 

 MoUusca which either bore tubular dwellings in rocks, wood, 

 . &c. or live in testaceous tubes, their shells being consequently 

 destitute of the hinge ligament. The action of opening and 

 shutting the valves being limited to the narrow space to which 

 they are confined, or else the valves themselves being soldered 

 into the tube, renders it unnecessary for them to have a liga- 

 ment to keep them in their places. The genera Pholas, Tere- 

 dina, Fistulana, and Septaria, belong to this family, which 

 corresponds in part with the families Tubicolaria and Pholadaria, 

 of Lamarck. 



ADNA. Leach. One of the genera separated by Leach from 

 Pyrgoma, and characterized as consisting of an upper valve, sup- 

 ported on a funnel-shaped base, which is not buried in the coral 

 to which it is attached, like Pyrgoma, but is seen externally. 

 The operculum consists of iowc valves. British Channel and 

 Mediterranean. Adna Anglicum, PI. i. fig. 2. 



ADNATE. A term applied by some authors to those shells belong- 

 ing to the family of Unionidse, which have the valves joined 

 together at the dorsal margin, not like other bivalves, by a dis- 

 tinct ligament, but by the substance of the shell itself, the valves 

 appearing to grow together in such a manner that they cannot 

 be separated without one of them being broken, as will be seen 

 in our figure of Dipsas plicatus, fig. 142. This circumstance has 

 been made the foundation of specific and even generic distinc- 

 tions, for which however it is insufficient, because many species 

 which when young are " «rfwa^e," when fully grown have their 

 valves joined together only by a ligament. 



