296 Messrs. P. H. Carpenter and R. Etheridge, Jun., 



Now in the Palteozoie Crinoids tlie symmetry of the calyx 

 is always disturbed by the presence of an anal or azygos side. 

 This may be indicated simply by the presence of an anal 

 opening, which notches one of the oral plates, as in Phimo- 

 crtnus, Haplocriniis, &c., or by the presence of a single anal 

 plate, as in Belemnocrinus, which in other respects has such 

 a close resemblance to the recent RMzocrinus^ or more com- 

 monly by the fact that one of the basals and two of the 

 radials differ from their fellows in size and shape so as to 

 give room for the system of anal plates wliich separates two 

 of the rays, or in some similar manner. 



Even in cases where the radials are closely united all round 

 and the general contour of the calyx is perfectly regular, a 

 want of symmetry is indicated by the inequality in the 

 numbers of basal and radial plates. This is the case, for 

 example, in Eucali/jHocrinuSj which has live radials but only 

 four ])asals. 



Lastly, in those Palasozoic Crinoids which have divided 

 rays the position of the axillary joint is by no means so fixed 

 as in the younger types. The rays may fork on the first 

 radial, as in Allagecn'nus j or the axillary may be as many as 

 six joints beyond it, as in Poteriocrinus radiatus^ or in any 

 intermediate position. 



Taking all the above facts into consideration, we are in- 

 clined to think that the Pala^ocrinoids do constitute a group 

 that is distinguished from the more modern types by an 

 assemblage of very definite characters, perhaps the most con- 

 stant of which is the distinction between the perfectly sym- 

 metrical calyx of tlie Mesozoic and recent forms, and the more 

 or less irregular one of the Palaeocrinoids. We suggest 

 therefore that the two groups should be distinguished as the 

 Palfeocrinoidea (Wachsmuth) and Neocrinoidea (nob.), or as 

 Irregularia and Regularia. The old terms Articulata and 

 Tessellata are meaningless, as we have shown above, while 

 the name *' Stomatocrinoidea," proposed by Wachsmuth, is 

 long and cumbersome ; and we are by no means sure that 

 some of the Palgeocrinoids did not have an external oral 

 opening. 



Whatever name be adopted for the Paleeozoic Crinoids, they 

 are of the highest interest morphologically, owing to their 

 presenting so many embryonic characters. These may be 

 briefly summarized as follows : — 



1. The great development of the orals, which sometimes 

 form a closed pyramid. 



2. The frequent presence of a more or less perfect vault 



