1890.] NATURAL SCIENCES OF PHILADELPHIA. 375 



brachials when they ure not. In either case they will ulso take the 

 special a])pellation given by Carpenter, viz., costals,cUdichals, pa/mars 

 etc., which will be either fixed or free as the case may be. We ])refer 

 to use the term post palmars, however, for all plates beyond the 

 third bifurcation, whetlier there be further branching or not, and 

 applv free to all brachials that are free from the calyx, so that in 

 the Inadunata all plates beyond the radials are free brachials, 

 whereas, according to Carpenter's idea, in a frequently dichotomiz- 

 ing form like CyatJwcrmus the term would only be applied to the 

 joints of the last slender branches at the tips of the arms. In the 

 Camerata we will have one or more orders of fixed brachials, as the 

 calyx extends variously to the distichals, palmars, or post palmars. 

 To correspond with these terms and conform to the ideas of the fore- 

 going discussion, it will be advisable to designate the different per- 

 isomic plates as follows : 



Interradials, all plates interradially disposed in the calyx. 



Interbrachials, a general term for all plates between the rays above 

 the radials. 



Interdistichals, the plates between the first divisions of the ray. 



Inierpahners, those between the second divisions of the ray. 



Interambulacrals, the plates between the ambulacra. 



Let us now consider the anal plates, which take such an impor- 

 tant part in the phylogeny and classification of Palaeozoic Crinoids. 

 The term " anal plate " has been used by some writers indiscrimi- 

 nately for all interradial plates of the posterior area, while others 

 restrict it to the plates directly or indirectly connected with the anus. 

 We apply the term only to the latter plates, and only to those tak- 

 ing part in the dorsal cup. All others are plates of the anal tube or 

 the ventral sac. 



The anal plates in all Camerata, when present, occupy the median 

 line of the posterior area so as to divide the interbrachial plates into 

 two equal sets, and in rows containing an odd number splitting the 

 middle plate into two pieces, even in cases when no anal plate is in- 

 serted between the segments. The latter is the case in all Actlnocri- 

 nites, in which the first interbrachial row at the posterior side invari- 

 ably consists of two plates as against one in each of the others; but 

 all have an anal plate between the radials, and a second one in the 

 second interbrachial row. In the Batocrinites, and in all other Ac- 

 tinocrinidae and Glyptasteridae, there are two interbrachial pieces 

 above the first anal, which enclose a second anal j^iece. The Hexa- 



