LIST OF PLATES 



Plate I. 

 TUNICATE, OR LEATHER-BAG MOLLTJSCA. 



1. Pelonaia corrugata, floating or living in the sand. 



3 a. CyntJiia aggregata, attached in groups when full grown. 



2 b. The same in a young state, when free like Pelonaia. 



3. Aplidiiim fallax, many individuals enclosed in each bag. 



4. Clavell'ma lepadiformis, individuals attached to each other by 



a basal thread. 



5. Ascidia mentula, attached to the rock singly. 



6. Botryllus polycyclus, individuals united in star-like bodies. 



Plate II. 

 PHOLADID^, OR BORERS. 



1. Pliolas dadylus, imbedded in the rock. 



2. Valves belonging to the back of the hinge, termed accessory 



valves ; they are formed, in many species of Pliolas, after 

 the animal has attained maturity. 



