223 



longitudinal ridges. It inhabits the laminarian and coralline 

 zones in Massachusetts Bay. The serration of the rostrum may 

 be mentioned among other characters which distinguish it from 

 A. stirhynchus. 



Mr. Stimpson also made some observations on the re- 

 markable worm Chcetopterus pergamentaceiis Cuv. which he 

 had found in North Carolina, it having been previously 

 known to occur only in the Antilles. 



June % 1852. 



The President in the Chair. 



Dr. Burnett said, that he had recently had an opportu- 

 nity, while in the Southern States, of examining the struc- 

 ture on which the extreme brittleness of the tail of the 

 Glass Snake, Ophisaurus ventralis, depends. 



It is a well-known fact that a very slight blow causes this 

 reptile to break in small pieces. This seems to be the result of a 

 reflex action from the spinal cord ; for after the tail is detached 

 if the spinal marrow in this portion be irritated, it breaks into 

 several pieces. On careful dissection, with the aid of the micro- 

 scope, Dr. Burnett had found that the muscles rising from the 

 vertebrae do not pass from one to another, but part of the fibres 

 are inserted into the skin, while others running parallel with 

 the length of the animal, terminate midway between one verte- 

 bra and the next, being dovetailed, as it were, between the fibres 

 sent to meet them from that vertebra, and attached to them only 

 by myolemma. When the division of the animal takes place, 

 therefore, there is no rupture of muscular fibre, but a separation 

 of one layer of muscles from the adjoining one. The detached 

 portion is said to be reproduced in a year. Dr. Burnett had 

 noticed the same phenomena in the Blue Tailed Lizard, Scincus 

 fasciaius, of the Southern States, depending on the same cause. 

 In all Lizards, during the breeding season, the tail is very liable 



