388 EXPLANATION OF THE PLATES. 



Fig. 



[a. Litliotrya dorsalis, (nearly twice nat. size), with the 



basal calcareous cup adherent; 

 (#), rostrum on same scale, 

 seen externally. 



1 ;/ ,, rostrum and the rostral corners 



of the two scuta, together 

 with a small portion of the 

 subjacent membrane of the 

 peduncle, with its calcareous 

 scales ; viewed externally, 

 greatly magnified, showing 

 the inferior crenated edges 

 of the scales. 



\ c \ 5 , „ basal calcareous cup, one and a 



half the natural size ; this is 

 the largest specimen which I 

 have seen. 



2. Litliotrya Nicobarica, (magnified nearly twice ;) at- 



tached to the rock, copied 

 from Reinhardt; (#), rostrum 

 on the same scale, with the 

 other valves, seen externally ; 

 (b), section of the row of discs; 

 (c), extreme point of the pe- 

 duncle, extending beneath 

 the row of discs. 

 2d. Rock bored by Litliotrya Nicobarica, showing the 

 row of calcareous discs, copied from Reinhardt. 



3. Litliotrya cauta } magnified between seven and eight 



times ; (a), scutum ; {b) 9 tergum. 



3c. „ „ latus, greatly magnified. 



2>d. „ „ uppermost scales of the peduncle, 



greatly magnified. 



Se. „ „ star-shaped discs of hard chitine, 



supported on a peduncle of the 

 same substance, taken from the 

 lower exterior surface of the pe- 

 duncle, very greatly magnified. 



