332 PROCEEDINGS OF THE ACADEMY OP [1885. 



sistent in principle to search for " parabasalia " among the plates 

 of the first ring, for basals and " parabasals " are not placed beside 

 each other, but the latter rest upon the ring of the former. We 

 doubt if Polypeltes possessed any such plates as " parabasalia," 

 at least not among the plates of these two rings. It is probable 

 that the plates of the inner ring, like those of the outer, were 

 parti}' radials and partly interradials, while the basals were hid- 

 den from view by the column. In support of this view it is well 

 to compare the plates here exposed with those represented in 

 allied genera. 



According to description, the ten bifurcating radials are suc- 

 ceeded by two rows of from four to five plates, consisting of 

 higher orders of radials ; the upper series bifurcating, giving off 

 another order of radials, and these the primary arms, which 

 branch after becoming free. Comparing the different portions of 

 the rays with the same parts in Abacocrinus and Corymbocrinus, 

 we find the form of the radials, their proportionate size, and even 

 the construction of the arms and their mode of branching, almost 

 identical with those two forms, provided we compare the ten 

 lower radials in Polypeltes with the ten rows of secondary radials 

 in Abacocrinus and Corymbocrinus. The main difference is that 

 the latter genus has but one bifurcation in the cah'x above these 

 plates, while the former has two, and consequently twice the num- 

 ber of primary arms, a difference only of specific value. From 

 the fact that Polypeltes has an extra bifurcation, and twice as 

 man}- primary arms as the other two genera, it might be asserted 

 that it has exceptionally ten primary ra\'S'instead of five, and ten 

 interradial spaces, but that is not the case. It has been stated 

 that the ten radials are laterally disconnected, and separated on 

 the one side by a single plate, and on the other by two larger 

 pieces. The two larger ones are followed by numerous other 

 plates, which, arranged in two rows, extend to the lower portions 

 of the arms, and enclose these within the calyx, while the smaller 

 plate at the other side stands perfectly isolated, surrounded on 

 all sides bj radials. That the former represent the plates of 

 five interradial series, and the single piece an axillary plate, has 

 been already stated, and this proves very clearly that Polypeltes, 

 like other Crinohls. has but live main rays, that the ten axillary 

 pieces in Angelin's figure represent 1X5X2 secondary radials, 

 and that the specimen must have somewhere primary radials. 



