NO. 1846. ON CERTAIN ELEUTHEROZOIC PELMATOZOA—KIRK. 93 



a filling out of the reentrant angle, but a concomitant resorption 

 of the proximal portion of the plate which rests within the angle. 

 K we take a monocyclic crinoid with a tripartite base we do not 

 say that there can only be three basals present, because there are 

 no signs of sutures or reentrant angles, and we can only see three 

 elements. If such a statement can not be applied here, wherein are 

 we justified in making the same assertion in regard to the proximal 

 circlet of TJintacrinus? 



On page 33 and elsewhere Springer states that there is no evidence 

 of fusion. Wliy does not his Plate 2 show practically every step 

 in such a process ? On Plate 9 will be found reproduced the impor- 

 tant stages figured by him. Figure 7 shows clearly that fusion of 

 one sort or other must have taken place. It is evident that there 

 is a single unfused infrabasal and one plate consisting of two fused 

 infrabasals. It is not necessary at this point to determine the 

 composition of the third plate, although we know that it must be 

 either the centrale alone or the centrale with which the other two 

 infrabasals have fused. The important fact is that there is a tend- 

 ency toward fusion among these plates just as we foimd that there 

 was a similar tendency among the plates of the proximal circlet of 

 other crinoids. If there be such a tendency toward consolidation, 

 is it not highly probable that the plates will not only fuse among 

 themselves, but also with the centrale? If so much be granted, it 

 is very easy to explain the various bases figured, which are other- 

 wise so puzzling. 



Figure 11 shows the regular ''monocycHc" base with the centrale 

 of maximum size. Figures 1 and 2 show the normal dicyclic base. In 

 figure 5 we find that one infrabasal has fused with the centrale. 

 The four other infrabasals are present, three being relatively small, 

 while the other is quite large. In figure 6 we see that two of the 

 infrabasals have fused with the centrale. Figure 7 shows a modi- 

 fication of the process. Here the centrale has fused with two of 

 the infrabasals, the resultant plate probably being represented by 

 the largest plate of the tliree — that on the upper left-hand side. 

 In addition, two of the infrabasals have fused, forming the plate 

 next in size. A fusion of the centrale and two infrabasals and the 

 remainmg unfused infrabasals would most certainly give the form 

 represented in figure 8. A further fusion of these two elements 

 would result in an UTegular plate, which would gradually acquire a 

 more symmetrical form by a process of accretion in some parts and 

 resorption in other parts, combined with similar processes acting on 

 the adjacent faces of the basals. 



Apparently the coalescence of the infrabasals and centrale took 

 place in no definite order. In figure 7 two infrabasals fused together, 

 while the centrale fused with two others. Another variation is to 



