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362 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
Calyx rotundate ; anal tube moderately 
small, about central; arm openings twelve 
to twenty; arms long, single or paired, 
often in the same species; respiratory 
POKES MOteeMISTOLC pape. eee TYE en 
2. ANUS WITHOUT A TUBE. 
a. Calyx lobed ; arms arranged in groups. 
Calyx more or less elongate. 
Arms heavy, one from each opening. 
Arms ten, recumbent on the dorsal cup ; pin- 
FaRDUWEKS) ala uta} Velo Wares. Nig EO ie wae Se ee 
Arms one only from each opening, erect, 
Tagen ANC Avevee ee ah ee wl et A 
Arms slender, paired ; upper arm joints 
spiniferous ; posterior oral and proximal 
radial dome plates extended into spines . 
b. Calyx hemispheric or pyramidal. 
Dorsal cup from very shghtly convex to 
concave; arms heavy. Orals and radial 
domemprates: PrOmanent aes 9 eM cus. 
B. ARMS UNISERIAL. 
1. BASALS THREE. INTERBRACHIALS NOT NUMEROUS. COL- 
UMN ROUND. 
a. Arms delicate, joints cuneate, alternately arranged, 
OniggamterlockimesabatinemtiS"s Waa fs. Hs) aes s&s 
b. Arms heavy, jomts quadrangular. 
PASM SUC RRM MG Reas ute Pw die wm ato, Sat pe 
AnmMsemOonre tiamutemas Wat. ee, 8 
2. BASALS FOUR; COLUMN QUADRANGULAR. 
Arms slender, joints cuneate; plates deli- 
cate and highly ornamented. Interbrach- 
ials and interdistichals very numerous . 
IT. 
VENTRAL DISK COMPOSED OF SMALL, IRREGULARLY ARRANGED PLATES, 
WITH OR WITHOUT ORALS. ARMS GENERALLY BRANCHING 
EIEN ONG NUNES Asin oxen Sg RR ME Sales eee Memon te ae wy 
A. ARMS BISERIAL FROM THE CALYX UP. 
1. Basals three; anal area wide. 
Calyx elongate, urn-shaped ; plates thin and 
elongate; arms grouped. Orals indistin- 
guishable. The column with large cen- 
URAC Aly ower Rete wee Sas Paces, 
Calyx depressed globose, plates short and 
heavy. Arms branching, given off in 
pairs, their facets contiguous; orals gen- 
erally represented; central canal large . 
Calyx low, strongly lobed at the arm regions, 
plates thin, highly ornamented. Arms 
arranged in clusters. Central canal of 
TANG TOKEN SE NO IAS) WN AER dT eee 
Dizygocrinus. 
Barrandeocrinus. 
Aorocrinus. 
Dorycrinus. 
Agaricocrinus. 
Acacocrinus. 
Habrocrinus. 
(?) Desmidocrinus. 
Compsocrinus. 
PERIECHOCRINITES. 
Periechocrinus. 
Megistocrinus. 
Genneeocrinus. 
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