72 



Dr. G. also read a paper on Mytilus edulis, showing its 

 powers of locomotion, and exhibited specimens in illustra- 

 tion. 



It is every where stated, that when the byssiferous mollusks be- 

 come once attached, they have no power to detach themselves. 

 So far from this, Dr. G. showed that they change place with great 

 facility. The specimen he exhibited had raised itself up the side 

 of a glass jar, three inches in a single night. To do this, the ani- 

 mal first stretched out its finger-like foot to its greatest extent, and 

 attached a fibre, and drew its body within the shell as much as 

 possible, by which the whole was raised about three fourths of an 

 inch. Numerous fibres were then fixed in a radiating manner, 

 until sufficiently secure, and then the whole of the pencil of radiat- 

 ing fibres forming the preceding attachment was thrown ofFin a mass, 

 at the foot, the ends being still held together by a sort of knot.* 



In Griffith's Cuvier, it is advanced that the Byssus " consists of 

 an assemblage of muscular fibres, dried up in a portion of their 

 extent, but living and contractile at their origin." The differing 

 length of the threads, 2 or 3 inches, according as their point of 

 attachment is more or less distant, their indestructibility by mace- 

 ration in water, and some other particulars, would invalidate this 

 idea. 



He alluded to a statement of Lamarck, that the shells of the 

 genus Modiola are always destitute of a byssus ; whereas, with 

 regard to the species found so abundantly on this coast, M. papu- 

 ana, Lk., this is notoriously an error. 



A Letter from Dr. Locke of Cincinnati was read, in 

 which he announced that he had sent to the Society a suite 

 of casts of Trilobites, exhibiting the varieties found in Ohio, 

 and the adjacent region. 



Dr. E. Hale read extracts from a Letter from Dr. Sav- 

 age of Cape Palmas, announcing further contributions to 

 our Cabinet, consisting of parts of the Chimpanzee not 

 before sent, also Fishes and Reptiles. 



* In the Annalcs des Sciences for July and August, 1842, it appears 

 that the same fact has been observed by M. Marion de Proce of Nantes. 

 He erroneously states, however, that the fibres of the old attachment are rup- 

 tured, whereas they are cast off in a mass, as above stated. 



