PLATE 109. 



Page 



Pig. 1 & 2. AVIC0LA TEXTiLis, var. akknaria. 465 



1. An impression made in sandstone by the exterior surface of the Ainallcr or riglit valve. 



2. The imprint of the exterior of the left valve of this species. 



Fig. 3. AviCCIiA RKCTIC08TA. 466 



Fig. 4. Meqambovia bkllistriata. 467 



4. A cast of the loft valve, from a mould of the exterior in .sandstone 



Fig. 5 & 6. Megamboma lamellosa. 467 



5. The left valve of a specimen of this species. 



6. The left valve, showing a proportionally more extended wing than the preceding. 



