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Found in great quantity on Nantucket Shoals, adhering to stones 

 and shells, at depths varying from six to twenty-four fathoms. 



3. Sertularia argentea, Ellis. Varies in size from 3 and 

 4 inches to 1 foot and a half. Common at depths of from three 

 to five fathoms ; also found frequently on tlie heaches around 

 Cape Cod, where it is thrown by the waves. 



4. Sertularia plumea, Desor. Polypidom very fine, like 

 down ; stem very little branched. Cells opposite, very close. 

 Differs from S. rosacea, Johnst., in being much less branched. 

 Height 1 inch. Dredged from twenty-two fathoms near South 

 Shoal. 



5. Laomedea dichotoma, Lin. From half an inch to an inch 

 high. Attached to stones and shells. Found at a depth varying 

 from ten to fifteen fathoms, near South Shoal. 



ASCIDOIDIAN POLYPS OR BRYOZOA. 



6. Flustra truncata, Lin. Very abundant near South Shoal, 

 at depths varying from fifteen to twenty-two fathoms. 



7. Cellularia turrita, Desor. Polypidom dense, like a bush ; 

 stem orange colored, divided into a great number of branches, 

 so that each stem looks like a small tower or pyramid. Found 

 in depths varying from three to fifteen fathoms. Thrown in 

 great quantity on the beaches of the islands of Nantucket and 

 Martha's Vineyard. 



8. Cellularia DENSA, Desor. Polypidom very dense, bushy : 

 divided into a great many branches, which are brittle when dry. 

 Somewhat allied to C. aiicularia, Pallas, but differs in the form 

 of the cells, which are more simple. Dredged from a depth of 

 twenty-two fathoms near the South Shoal. 



9. Lepralia variolosa, Johnst. Very abundant on the 

 Shoals of Nantucket, at depths of from ten to twenty-five fathoms, 

 where it covers almost every stone and shell. Its color is of a 

 bright red, but it fades very soon after being brought to the sur- 

 face. 



10. Membranipora tenuis, Desor. Cells lobate, more elonga- 

 ted than in M. pilosa, Pallas, with a plain margin of a pale pink 



