Davknport. — Cristatella. 



PLATE IV. 



All figures, except Fig. 39, are vertical right-and-left sections, and all are magnified 



390 diameters. 

 Figs. 24-26. Three sections from a series passing from the oral to the aboral face 

 of a polypide of about Stage X., and cutting it in the planes indi- 

 cated by the lines 24-26, Fig. 13. 

 " 27-29. Three sections of a series cut from a polypide of Stage XI. The 



planes of section are indicated in the lines 27-29, Fig, 17. 

 " 30-32. Three sections, whose positions are indicated by the lines 30-32, Fig. 



18, cut from a polypide of Stage XII. 

 " 33-38. Six sections cut from a pclypide of Stage XIII. in the directions indi- 

 cated in Fig. 19 by the lines 33-38. 

 " 39. A horizontal section of a polypide somewhat older than that repre- 



sented in Fig. 18, and passing nearly in the direction of the line 43. 



