PLATE I. 



Fig. 1. SriKIIEK EXOELMANXI 



1, a. Outline showing the form of the a 

 1, b. A side view. 



l,c. Dorsal view. 

 Fig. 2. Atrypaaspera? 



2, a. Ventral view. 



2, J. Dorsal view. 



Fig. 3. Producttjs ? 



3, a. Ventral valve. 



3, c. Dorsal valve. 



Fig. 4. SriiiiiKii Ttwiensis 



4, a. Ventral view. 

 4, b. Profile view. 



4, c. Outline showing area and foramen 

 Fig. •">. fcl'IRIFERSTRIGOSUS 



5, b and d. Dorsal views of same. 



6, b. Side view of sac 

 Fig. 7. Productts semisti 



7, a. A side view. 



7, b. Dorsal view of i 



Fig. 8. Productts mei.tisi 



Fig i>. 







le, showing position of the siphui 



