PLATE IV. 



Glyptocystites Logani (page 57). 



Figures la and \h are dorsal views of two specimens. 



" Ic, la and le are enlarged views of the interiors of three rhombiferous plates, 

 shewing that the pores penetrate through, and that each on the inside 

 is surrounded by an exceedingly thin elevated border. 

 " 1/. A portion of the ambulacral groove of the apex, and one of the pinnulae 



enlarged. 

 " \g. A fragment with two of the pinnulse. 



" \i and \j. Fragments of columns. The specimens are crushed, and do not 

 clearly shew the spiral arrangement. 



Gr. LoGANi, var. GEACiLis (page 59). 



Figure 2. Dorsal side of the only specimen collected. 



Glyptocystites Foebesi (page 59). 



Figures 3a and 36. Two views of the base of a specimen. 



" 3c and 3rf. Imperfect plates, to shew the character of the rhombs. 



'* 3d has the remains of four rhombs. 



" 3e is the basal plate of the right side. 



" 3/ is the hexagonal basal plate of the anterior side. 



" Sg- and 3A, round columns, with the edges of the large joints pitted. 



