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August 18, 1852. 



Dr. A. A. Gould in the Chair. 



The Secretary read a communication from Mr. W. O. 

 Ayres, giving descriptions of two new genera and three 

 new species of Holothuria, as follows. 



During a recent excursion to Eastport, Me., I obtained several 

 specimens of a Holothurian, which is apparently not only unde- 

 scribed, but the type of a new genus. The generic characters 

 are, — Body vermiform, not provided with either suckers or 

 hooks, but having between the longitudinal muscles numerous 

 small tubercles which contain very regular, minute, calcareous 

 wheels. Tentacula ten, digitate. Oral circle of ten pieces, 

 without projections either upward or downward, each alternate 

 piece perforated. No muscular stomach. Genital tubes divided. 

 Respiratory trees wanting. 



The wheel-like deposits suggest the name 



Trociiinus Ayres. 



The species, from its color, may be called T. pallidiis Ayres. 



The largest specimens yet seen are not quite five inches 

 in length, with a breadth of half an inch. The surface pre- 

 sents five rows, more or less perfectly developed, of " warts," 

 (Pourt.) which, when dry, look like small white scales. These, 

 under the microscope, are shown to contain multitudes of 

 beautifully regular wheels. Each wheel is perforated at the 

 centre, and provided with six radiating, broad, bevelled 

 "spokes;" the rim being strengthened with a waving ridge. 

 The largest are about one tenth of a millimetre in diameter. 



The intestine, of nearly uniform diameter, extends back- 

 wards, again forward, and returns straight to the anus, having a 

 little less than three times the entire length of the body. 



The oral circle resembles that of Synapta in the general 

 form of its pieces, and in their perforation, but differs in the 

 number (ten instead of twelve,) and in their exterior surface. 



