INVERTEBRATES. 355 



of the body is across the lips, where the section is strictly pentagonal, 

 while across the bjjsals it is obscurely triangular. Average length 

 and width, as taken from eleven specimens, as eight to five, actual 

 length from three to six-tenths of an inch. The surface of the test 

 is perfectly smooth, without ornamentation. 



Basals long, in form of an elongate cup ; column-like, extended at 

 the lower end; upper face somewhat excavated for the reception of 

 the radials, with an obtuse angle beneath their juncture. 



Radials moderately increasing in width to the sinus. The length 

 of the radial body equal to or surpassing its greatest length, 

 and equal to the length of the basals. The limbs occcupy 

 less than one-third the entire length of the plate, they are 

 slightly bent inward, those of two contiguous radials forming a tri- 

 angle, of which the horizontal side (between the lips of the adjoining 

 radials), is but little longer than the two lateral sides. At the anal 

 interadius. the upper angle is truncated by the anal aperture, and 

 the outer side of the pyramid is more sloping. Sinus short, and 

 remarkably deep. 



The oral plates are small, and are only partly exposed to view, 

 one half or more of each one being hidden beneath the radials. The 

 exposed part, which consists of barely more than what might be 

 called the lips of the mouth, is slightly projecting along the margin ; 

 it is in form rhomboidal, but the angle toward the radials is cov- 

 ered by the tips of the overlapping limbs. The concealed portions 

 are at the four lateral interradii placed beneath the large pyramids 

 which have been described; they are longer than wide, and their 

 distal end is somewhat extended outward and downward. The me- 

 dian portion of the plate is provided longitudinally with a canal, 

 which from its position may have connected the hydropires with 

 the outer vascular ring. The description of the oral plates is made 

 principally from a specimen, in which the greatest part of the ra- 

 dial limbs had weathered away, thereby exposing the parts below. 

 As seen in this specimen, the lateral sides of the concealed oral 

 plates give off the two inner hydrospires for each group, the first of 

 which, at several places, is preserved to its full length; the second, 

 however, is recognized only by a stump, and there is a notch for 

 the intermediate slit. The oral plate of the anal interradius is con- 

 structed near the mouth somewhat different from the orals of the 

 four regular sides ; the parts which there are covered by the limbs, and 

 form the oral ridges, take here a more inward direction, and com- 

 pose the sides and inner floor of a little cavity, which forms the 



