PALASTERINA PRIM^VA. 



227 



distinct large plates (mfero-marginalia), which are again succeeded by the small 

 accessory plates (only seen in side or oral view). A drawing is given (Text-fig. 158, 

 p. 221) to show the shape and ornament of these plates. The supero-marginalia 

 overlap and are what I have called "bent finger" shaped. The series outer to 



P < 



> D 



(h) 



(a) 



Am. 3 ■ 



Text-fig. 163. — (a) On right. Wash-drawing of the apical surface of the proximal ambulacralia of 

 Palasterina primxva (from Sedgwick Mus.). Am. u first ambulacral ; Am.,, second ambulacral ; Am. 3 , third 

 ambulacral. x 10. (6) On left. Lateral view of apical surface of adambulacralia. P., proximal'; D., 

 distal direction, x 18. 



this are very similar. If seen in position in side view they appear V-shaped. 

 Probably the shapes of both series may be derived from what I have called 

 the half-moon shape in the case of Uranaster (see p. 110). 



The ornament on the plates is very distinct from that of Schuchertta. On each 

 ossicle is a central eminence which carried a long spine. Small pustules, which 



J\m.Z 



VJ.V.V 



rt.TP. 



M.R 



Text-fig. 1(34.— Adoral view of the mouth-frame of Palasterina primmva (from Sedgwick Mus., no. 344). 

 Am. lt .), first and second ambulacralia ; Ap., apophysis ; M.P., mouth-angle plate ; n.r., groove for nerve 

 ring; w.v.r., groove for water-vascular ring, x 18. 



doubtless carried small spines, are scattered around this. A somewhat similar 

 ornament is figured by Schuchert for Promopalxaster bellulus and P. spinulosus 

 (1915, pi. xv, fig. 7 ; pi. xviii, fig. 8). 



Several specimens have the apical covering displaced and show the upper 

 surface of the ambulacralia. Text- fig. 163 gives such a view in the region of the 



