108 PROCEEDINGS OF THE ACADEMY OF [1887. 



In the Comatula larva, which shows a decidedly bilateral symmetry, 

 there are five equal basals and five equal orals. In Thaumatoorinus, 

 although it has anal plates and a large proboscis, the basals and 

 anals remain undisturbed. The same may be said of the basals of 

 the Palaeocrinoidea and Blastoidea; among which not a single in- 

 stance is known where the basal ring contains either anals or radials, 

 contrary to the proximals, among which nearly always anals and often 

 radials are enclosed. This shows that the presence of such plates, 

 if the proximals in those groups represent the orals, and the latter 

 the basals, would be totally at variance with the general rules of the 

 class both as to orals and basals. 



The anal plates of the apical side either abut directly against the 

 radials, or are placed between the interradials. In most of the Cam- 

 arata, the first interradial at the azygous side is split into two halves 

 by the first or second anal piece. In others, the second anal is want- 

 ing, but the interradial is composed of two parts as if the anal were 

 present. In a few groups there are no anal plates whatever, and 

 the arrangement of the plates at all five sides is alike. 



The same variations as among the interradials are found in the 

 arrangement of the proximals, * of which the four large plates corre- 

 spond to the calyx interradials at the four regular sides. The two 

 smaller proximals, which occupy the azygous interradius, either are 

 placed between two radial dome plates or they abut against two of 

 the larger proximals, enclosing generally an anal plate but this 

 may be absent or pushed downard. 



As yet, we have not observed a single instance in which there were 

 five plates around a central one, but should it occur, which we think 

 is very possible, we doubt if Messrs. Etheridge and Carpenter, although 

 finding at last their "simpler form," will be able to make much 

 out of it in support of their theories. 



We stated heretofore that fig. A on p. 72 of the Blast. Cat. is 

 erroneous, and this, to some extent is the case with fig. B on the 

 same page. We never saw a Platycrinus with a single interradial, 

 all having three (or more), arranged transversely. Besides, the 

 figure is misleading in not giving the central piece and the so-called 

 radial-dome plates. If these plates had been added, as they should 

 have been to represent the case properly, it would show that the 

 radial-dome plates are placed opposite the radials, the proximals 

 opposite the interradials, and that the central piece takes orally the 



*For the arrangement of the proximals see Revision Pt. Ill, pp. 47 to 50. 



