OYSTER-BEDS OF LOUISIANA. 93 



occur in sufficient inimbers to cause very great damage, but one man 

 stated that lie liad had almost an entire lugger-load of oysters, from 2 

 to 3 inches long, destroyed by an unknown enemy, which had crushed 

 the thin edges of the shells. The appearance of specimens of shells 

 taken in Quarantine Bay and said to resemble those just mentioned 

 leads to the suspicion that the destruction was wrought by the crab 

 under discussion, the entire distal halves of the shells being wrenched 

 and crushed. 



Boring-sponge. — Upon the oyster-beds of Louisiana occurs a boring- 

 sponge closely related to, if not identical with, the Cliona sulplmrea 

 found on the oyster-beds of the North. Cliona sulplmrea in its mature 

 stage forms large yellow masses sometimes more thauG inches in diam- 

 eter. During the investigations in Louisiana waters none of these 

 massive forms were found, but many of the dead shells and some of the 

 living ones were honeycombed by the galleries of the young sponges, 

 which sometimes projected, as mushroom-shaped papillae, nearly a 

 quarter of an inch above the surface of the shells. This was particu- 

 larly the case on the extinct reefs of Barataria Bay and other places 

 west of the Mississippi Eiver, where it occurs usually associated with 

 the coral, Astrangia dance, exactly as it does in places on the Atlantic 

 coast. It is thought that this sponge does little harm to the oysters of 

 Louisiana, but, in connection with the boring mollusk Martesia, it per- 

 forms an important function in cleaning the reefs of old shells, which it 

 corrodes and dissolves as its galleries extend. By the combined action 

 of these forms the old reefs are practically eradicated in the course of a 

 short time, and unless they become restocked with spat within 3 or 4 

 years they are placed beyond the possibility of natural rejuvenescence 

 by the destruction of the cultch. It is rather remarkable that this 

 sponge does not attack the shells on the shell-banks, such as are found 

 in Barataria Bay. 



Martesia cuneiformis. — This form is extremely abundant on the coast 

 of Louisiana, especially upon the oyster-beds of St. Bernard Parish. 

 It is a small species of boring-clam, which, during infancy, bores into 

 the oyster shells, excavating a tiny cell from which it does not again 

 emerge. As the clam increases in size the cell is enlarged, eventually 

 becoming an egg-shaped cavity half an inch in its major axis and com- 

 municating with the exterior by a small pore about -oV inch across. 

 Often these are so closely arranged as to be almost in contact, and the 

 oyster shell is so weakened that the outer part will scale off with a 

 slight blow. This delamination appears to often take place naturally, 

 the bases of the ovate chambers showing on the remaining parts of the 

 shell as a collection of rounded pits, often mistaken by the oystermen 

 for either incipient or abortive borings of the snail, Purpura. These 

 animals can not be classed as true enemies of the oyster, and, in fact, 

 they do it practically no injury, as the chambers rarely penetrate the 

 shell, and even then are readily closed, and the delamination spoken 

 of is not sufficiently profound to seriously injure the shell. The oyster 



