ADH^HENTIA. 387 



arranged at the same distances ; of these the contents are 

 distinctly cellular, resembling cells in the interior of glan- 

 dular folHcles. They lie in the perforations of the shell, 

 and often on its inner surface, having distinct and inde- 

 pendent terminations on the internal surface of the shell. 

 The surface of the mantle, when carefully examined, is 

 found to be studded with minute cells in that part which 

 comes in contact with the shell, and each one exactly cor- 

 responds in size and aspect with those contained in the 

 tubules. The purpose designed by such a curious structure 

 is at present a mystery ; it is, however, without doubt, of 

 considerable importance in the economy of the moUusk. 



This beautiful arrangement requires, for its development, 

 to be magnified at least 150 diameters. 



"&' 



I^amily II. Adh^rentia. 



" Look on the frame 

 Of this wyde universe, and therein read 

 The endless kind of creatures which hy name 

 Thou canst not count, much less their nature's aime^ 

 All which are made with wondrous wise respect, 

 And all with admirable beauty deckt." — Spenser. 



In this family the shell adheres immediately, though pro- 

 vided with a muscular tendon, that passes through a perfo- 



2 c2 



