SECTION IV. 1882. ere? Trans. Roy. Soc. CANADA. 
XII—A Classification of Crinoids. 
By Proressor E. J. CHAPMAN, Ph.D. 
(Presented May 26, 1882). 
The following classification of the Crinoidea is based essentially on the presence or 
absence of a canaliculated structure in the calyx and arm-plates. Three leading divisions 
are thus recognized. In one, the plates (apart, of course, from the stem segments) are with- 
out internal canals; in the second, the arm-plates are perforated internally ; and in the 
third, a system of canals radiates from the base of the calyx to the extremities of the arms. 
The secondary and subordinate sub-divisions of the classification have been worked out to 
bring readily under grasp the more salient or broadly-distinctive features of all the better 
known families and types of Crinoids ; and as the common names of the families (which 
cannot, of course, be altered) embody very little indication of these features, an additional 
grouping into sections has been adopted—each section bearing a characteristic designation. 
It must be understood, however, that the brief definitions attached to these sections are 
merely distinctive, and have no pretensions to be considered diagnostic in the proper sense 
of the term. Finally, as regards genera, the more typical only are enumerated, but these 
include all of ordinary occurrence. 

DIVISION I —EMEDULLATA (—Tesselata, pars.) 
Calyx-plates and arm-plates without internal canals: the calyx-plates mostly of mod- 
erate thickness, with straight or only slightly indented edges of junction. Genera, typi- 
cally, Palæozoic ; two, only, Cretaceous ; none living. 
GROUP 1—AMPLICINCTA : 
Calyx-plates large, or few in number: Radials in a single horizontal zone. 
§ 1. Proclinata :—Arms unequally developed : calyx pensile ; 
Fam. 1. Cheirocrinide (Typical genus, Cheirocrinus, Up. Sil. to Carb.). 
§ 2. Attenuata :—Arms very long and thin, simple, equally developed ; typically, with 
elongated joints, no pinnulæ. Calyx small; upper edge of radials deeply indented. Basals 
5 oF 35 
Fam. 2. Pisocrinide (Typ. genera, Pisocrinus, Up. Sil.; Nematocrinus, Carb.; Triacrinus, 
Dev., Carb. ; Hybocrinus, Lr. Sil.; Haplocrinus (2), Dev.). 
§ 3. Spatiosa :—Calyx-plates, large; the radials deeply indented at their upper edge ; 
basals 2, or 2 + 1. Arms numerous, pinnulated ; 
Fam. 3. Platycrinide (Typ. gen., Platycrinus Up. Sil. to Carb.; Eucladocrinus, Carb.; 
Hexacrinus, Dev. ; Marsupiocrinus, Sil., Dey.; Coccocrinus (?), Up. Sil., Dev.). 
§ 4. Pinnigera :—Calyx-plates, large ; radials with more or less concave upper edge; 
basals, in two zones, 5,5; arms branched or simple, with long pinnule ; stem, round, 
pentagonal, or wanting. 
Sec. IV., 1882. 15 
