342 s. ooTO : 



which near the marginals arc similar in form to those of the 

 latter, but arc considerably larger and of a difièrent form on the 

 inner plates. For a plate with a pedicellaria, the arrangement of 

 the granules is as follows (PI. XII, fig. 185) : along the border 

 of the plate is a row of small, rather closely set, marginal 

 granules ; in a large excavation in a subcentral position lies a 

 large pedicellaria, the valves of which are of the form shown in 

 ligs. 185 and 101 ; and between the pedicellaria and the marginal 

 granules, a variable number of large round or more or less 

 flattened conical granules, with a few additional smaller gran- 

 ules. The pedicellaria is almost always 2-valvate, but I have also 

 observed a 3-valvate one. On the plates without pedicellaria 

 the entire central area is covered with large conical granules, 

 which tend on especially larger plates to be more like the mar- 

 ginal granules both in form and size, though remaining larger 

 than they (Pi. XII, fig. 186). On none of the plates have I 

 observed more than one pedicellaria. The granules when removed 

 leave small excavations on the plates like rain-prints on soft 

 mud, and the pedicellaria? leave rectangular pores. 



Abactincd plates. — The abactinal plates are closely set and of 

 very unequal size. The larger one, whose form can be well 

 observed, are more or less round and slightly convex. In the 

 arms a carinal series of somewhat larger plates can be made 

 out, bat it is merged in between the other plates in the disk and 

 can not be traced to the central elevation. The plates in the 

 interradial depressions are generally larger than those of the 

 central and radial elevations, but the plates bordering on the 

 superomarginals are very small. Here and there, where the 

 plates are more separated from one another they are seen to 



