320 



DR. n. LYSTER JAMESON ON 



of the muscular iusertions or singly in the non-muscular parts of 

 the body- wall and mantle. 



Text-fig. 40. 



col^ 



Tiac. 



TICLC. 



ar. 



cun. 



TULC. 



B, 



A. The irregTilar columnar and amorphous substances, shown at col. in text-figure 39. 



nac, nacreous lining of the shell ; nac' , nacre deposited shortly after intro- 

 duction of nucleus, passing over into the repair-substance (^r.) ; nac." , nacre 

 continuous with the layers investing the nucleus ; col., col.' , columnar repair- 

 substance; a»i., amorphous repair-substance. X 35. 



B. The fan-shaped mass of repair-substance, shown at col.' in text-figure 39. 



5«M., the introduced "nucleus"; nac, the original nacreous lining of the 

 shell ; nac! , the first layers of nacre, separated after the introduction of the 

 nucleus ; col., columnar repair-substance ; am., amorphous repair-substance ; 

 gr., granular matter, perhaps of extraneous origin. X 100. 



