﻿240 ■ NEW YORK STATE MUSEUM 



smallest plate in the figure. The fold on the other side came between 

 r. post. IB and r.ant.IB and both of these plates are larger than the 

 others and have undergone excessive widening at their orad ends. 

 The variation in rate of growth in this part of the theca is shown 

 by the following table : 



Table 10 



Height Length of two orad sutures 



r.ant.IB 3.8 mm 4.2 mm 



ant - IB 3-5 3-3 



Unt.IB 3.5 3.2 



l.post.IB 3.6 3.9 



r.post.IB 3.7 4.4 



Just above the place of most rapid growth lies r.post.B and this 

 plate is quite distinctly folded vertically. Had this folding been 

 due to compression after death, the RA would show signs of dis- 

 placement. Instead of this it shows the peculiar extended growth 

 to the right which gave it the appearance of possessing a fifth 

 angle. The folding and bowing out of the center of r.post.B which 

 is still further accentuated by its central knob, is readily seen in text 

 figure 6 and is therefore normal to the species. This compression 

 reminds us of the more markedly folded plates of the Anomalocys- 

 tidae, but our theca is compressed at right angles to the plane of the 

 thecal apertures and not in this plane. With five basals, but one 

 would be subjected to this folding. On examining these BB for 

 postmortem changes, we find only a very slight disturbance of 

 r.ant.B and this is shown in text figure 8. We may now recall the 

 evidence found on p. 228 where it was shown that r.post.R had been 

 adding stereom to its right side more rapidly than r.ant.R had to 

 its left. 



The tegmen and plates above the anus. This region is taken 

 next for the purpose of completing the evidence for flattening dur- 

 ing ontogeny. The series of plates over the anus form a long line 

 in which the madreporite is the most prominent, but plate 7, figure 

 2, shows that none of these plates have been displaced and their 

 sutures show that no shortening of this line was possible. The 

 widened anal area has so thrust the arms away from it as to cause 

 those of l.post.R and r.ant.R to lie almost opposite each other. 

 This may be seen in plate 7, figure 1. The five food grooves do 

 not run to one center but clearly express the hypothetical primitive 

 food grooves with the forking of the right and left rays (see Bather, 

 op. cit. p. 11). L.post.O and r.post.O have an acute angle at their 



