EXPLAN'ATIOX OF PlATE 4 



Figs. 1, 1a. — Lepela caeca (Miiller) from 132 feet: 1, apical view; 2, side view, showing 



straight anterior and convex posterior ends. 

 Figs. 2, 7. — Puncturella noachina (Linnaeus) from 184 feet: 2, interior view, showing props 



at sides of septum and depressions in front of tiicm; 7, side \'icw, showing straight 



anterior and convex posterior ends. 

 Fig. 3. — Cylichna occulta (Mighels) from plankton tow near shore (net touching bottom), 



July 13, 1950. 

 Figs. 4, 5. — Alar gar itopsis f grosvenori (Dal!) from 175 feet. 

 Fig. 6. — Retusa umbilicala (Montagu) from 477 feet, a specimen without an umbilical 



perforation. 

 Figs. 8, 9. — Margarites vahli MoUer: 8, from 477 feet; 9, from 184 feet. 

 Fig. 10. — Mysella sovaliki, new species, from 741 feet, left and right valve, respectiveh'. 

 Fig. 11. — Musculus corrugatus (Stimpson) from 204 feet, a young specimen 7.3 mm. long. 

 Fig. 12. — Thyasira flexuosa (Alontagu) var. sarsi Philippi from 162 feet. 

 Magnification: 1, X 4; 1a, X 1.6; 2, 3, X 5.5; 4-6, 10, X 5.4; 7-9, X 5.3; 11, X 7.5; 12, 



X 6.4. 



