277 





5 Fig. 112 6 



1. Conifarison of extreme variates of each of the series shown in fig. 109; Goat Island (left), 

 Dumbarton (center), and Crockett (right). X 5. 



2. Details of denticulation of a portion of the anterior median area of a shell from Goat Island. X75. 



3. The same, from Dumbarton. 



4. The same, from Crockett. 



5. Shells from stagnant aquarium, discolored black by action of sulphur bacteria. X4. 



6. Head of Teredo, with body and shell colored blue as a result of working in redwood in vicinity 

 of an iron nail. X 4. 



