1885.] NATURAL SCIENCES OF PHILADELPHIA. 313 



This was based upon an incorrect understanding of the plates. 

 That it is not the case in Platycrinus is readily seen by our fig- 

 ures on pi. 7. Even the most simple form has three interradials, 

 horizontally arranged, all supported by the first radial plates, and 

 we are convinced that three, or a greater number of plates, are 

 found in all other Platycrinidae, and all Hexacrinidae. Wherever 

 we have observed them, the middle plate is larger, and rests upon 

 the juncture of two first radials, the outer ones upon their upper 

 face, meeting laterally the higher radials. The larger number 

 occurs in forms with flattened disc and wide, spreading rays. 



The presence of three or more pieces in the first row, which 

 evidently represent the first, second, and perhaps third ranges 

 of interradials in other groups, is morphologically of consider- 

 able importance, as it seems to have produced, to a large extent, 

 the structural peculiarities of the two families. It is evident that, 

 owing to the great width of the interradial areas, the succeeding 

 radials could make no connection with the higher interradials, 

 and the rays thereby became isolated, and remained permanently 

 in a more or less embryonic state. Three interradials seem to 

 have been represented also in Coccocrinus, as shown in Roemer's 

 figure 5 C of G. bacca, although they are not figured in his Cocco- 

 crinus rosaceus. 



We also refer to the Camarata the genus Barrandeocrinus. It 

 was made by Angelin, Zittel and De Loriol the type of a distinct 

 family, and this seems to be warranted b} r its exceedingly strange 

 form, produced principally b} r the construction of the arms and 

 the arrangement of the plates at the ventral side, although the 

 plates along the dorsal side are arranged similarly to those of 

 the Actinocrinidae. 



The Camarata, according to our classification, fall into ten 

 families : 



A. Keteocrinid^e. Base monocj^clic or dieyclie. Basals 4 

 or 5. Radials folded into strong tubular longitudinal ridges 

 along the median line of the plates. Interradial and interaxil- 

 lary areas deeply depressed ; resting upon the basals. They are 

 composed of a large number of ill-formed immovable pieces, 

 which continue to the ventral side, almost completely covering 

 the interpalmar areas, leaving but a small oral plate at the centre. 

 Azygous side wider; divided by a vertical row of rather large 



