STAUROCALYPTLS MICROCHETüS. 205 



free proximal ray is found to be soinewliat longer tlian any other 

 of the six. Length of rays, 120-143/-«; average tliiekness at 

 base, 10 p-. The S})icules form a eontinuous lacework whieli is 

 for the most part regularly (juadrate-meshed (PI. VIII., fig. 20). 

 It lies close over the parenchymalia, from which scarcely any 

 diactins can be distinguished as hypogastralia. 



The oxyhexasters may be distinguished as of two kinds, 

 though these seem to iutergrade into each other by transitional 

 forms. They may be said to differ in respect both of size and 

 general appearance. 



One kind (PI. VIII., fig. 21) is met with, not abundantly 

 but in moderate frequency, only in the proximity of the ectosome. 

 It is comparatively small and of a delicate appearance. Diameter, 

 68-100 /-«. From each short and slender principal there arise o- 

 o, thin and widely divergent terminals. 



The other kind (PI. VIIL, fig. 20) occurs in the choanosome 

 as well as in the endosome and is far commoner. Besides l)eing 

 larger, the terminals are somewhat stronger and the piincipals 

 usually so exceedingly short that they may be called abortive. 

 Diameter, 106-1 o6 /^-. The central node is frequently swollen to 

 a globular shape. The number of terminals to a principal is 

 usually 2, but may rarely be 3 or sometimes only 1. Hemihex- 

 actinose forms are of occasional occurrence. Hexactinose forms 

 were not found ; if thi-y occur at all, they must be very rare. 

 The terminals are nearly smooth or obsolctely rough. 



The (lisrodasters (PI. VIIL, iig. 23) are very abundant 

 subgastrally and a}iparently also in the endosome itself. I have 

 not found them in any other position. Diameter, 11 1-128 />«. 



