214 



The anal plates are small, polygonal, and covered with minute 

 tubercles. The anus itself is nearly circular in shape and is not 

 to be seen from an upper view, being placed on the upper part 

 of a broad cavity at the posterior extremity. The buccal open- 

 ing is hemispherical ; the plates which cover its membrane are 

 irregular in size, very much crowded, very thin and subconcave. 

 The star-shaped and apparently smooth area which surrounds 

 the mouth, is largely developed and the buccal star very dis- 

 tinct, although the pores are but few in number and irregular in 

 shape. 



The tubercles of the superior surface are generally very small 

 and uniform amongst themselves. They increase in size on the 

 lower half of the posterior extremity and below the subanal 

 concavity, to acquire their maximum on the middle region of the 

 inferior surface, on a cordiform and convex space behind the 

 mouth. 



The spines themselves I have not been able to study, as but 

 {e\v were left on the specimens in my possession, which may 

 hereafter be seen at the Smithsonian Institution. 



Mr. W. O. Ayres read a description of a new species of 

 Synapta, under the name Synapta pelhicidaj Stimpson and 

 Kiirtz, Mss. 



This species was brought from South Carolina by Mr. William 

 Stimpson, having been taken in the Sandy-mud Flat of Fort John- 

 son, where it occurs in considerable numbers. It inhabits holes 

 which " descend in a quadrant form, deeper than long, to about 

 a foot in depth. A smooth, round hole indicates the position of 

 each at low tide." (St. Mss.) 



The animal attains a length of twelve inches (with a breadth 

 of two fifths of an inch,) though it can seldom be obtained entire, 

 as it detaches piece after piece of its body upon the least dis- 

 turbance. This tendency to spontaneous division it possesses in 

 a much more remarkable degree than our northern *S. tenuis, 

 resembling in that respect the European species. It is of a pale 

 whitish flesh color, with the spaces occupied by the longitudinal 

 muscles of an intense white. 



The pieces constituting the oral circle are similar to those of 

 S. tenuis, though perhaps a little more elongated ; five of them 



