CLASS III 



CEINOIDEA 



207 



Order 3. INADUNATA Wachsmuth and Springer. 



Orinoidea in which the arms are free above the radials ; dorsal cnp liinited to 

 radials, basals, infrahasals when present, and anal plates; no interradials or inter- 

 hrachials except at the posterior {anal) side, and brachials never normally incorporated 

 in the cnp. All plates of the cnp united by close suture. Mouth snb-tegminal. 



Suborder 1. LARVIFORMIA Wachsmuth and Springer. 



{Haplocrinacea Neumayr ; Larvata Jaekel pars). 



Monocyclic (except Cupressocrinus). Calyx consisting only of basals {tvith or 

 tvithoid infrabasals), radials, and orals, without anal plates, and usually without 

 visible ambulacra. All plates immovably united by close suture. Arms non- 

 pinnulate, simple and uniserial (exception, the doubtful Stephanocrinus). Silurian 

 to Carboniferous. 



The simplest form of the Crinoidea ; containing only plates found in the larval or very 

 young stage of existing types, without any supplementary plates whatever except sucli as 

 may belong to an arm-like anal tube. They are usually small, one genus, AUagccrinus, 

 almost microscopic. Similar minute forms may yet be found in the pre-Silurian formations, 

 from which their absence thus far has been urged as an objection to the validity of the group, 

 considered as a phylogenetic representative of the larval stage. It must be admitted that its 

 limits are not very well defined, but the typical form is Haplocrinus. 



Family 1, Stephanocrinidae Wachsmuth and Springer. 



Monocyclic. Calyx cup-shaped, composed of three elongate basals, five radials, 

 and five orals, with ambulacra. Radials deeply forked ; the prongs formed by the 

 margins of two contiguous radials extending upward between the arms, in spinelike 

 processes. First costals semilunate and resting within a horseshoe -like concavity near 

 the outer end of radial incisions. Tegmen consisting of the orals, surrounding a 

 central space, which is roofed over by five greatly modified ambidacrals in form of 

 a flattened pyramid of triangrdar plates ; with anchylosed covering plates extending 

 outward to the arm bases. Anal aperture between posterior oral and interradial 

 process. Arms with one short hiserial trunk to 

 the ray, giving off slender biserial, non-pinnidate 

 side arms from the outer shoidder of each brachial. 

 Ordovician and Silurian. 



Stephanocrinus Conrad (Bhombifera Barr.) 

 (Fig. 308). This unique genus is an inter- 

 mediate form, variously considered by different 

 authors as a Blastoid, a Cystid, or a Crinoid. 

 The presence of branching biserial arms, as 

 pointed out by Wachsmuth and Springer, 



■■•, . ■',. .,, n • -J li.i,T_ urian ; Lockport, New York, o, Side view 



makes it unquestionably a UrinOld, altnOUgn of calyx, natural size ; b, summit aspect, 



not normal for the present group, in which it ^SbrUrawaylaft^erHa?^ °' "" 

 is placed on account of its simple and primitive 



type of calyx. The forked radials, resemblance of the orals to the deltoids, 

 and the orientation of the small basal in the right anterior position instead 

 of the left anterior as in other Crinoids with three basals, are all characters 

 which indicate a close relationship to the Blastoids. Ordovician ; Bohemia. 

 Silurian ; North America. 



Fig. soy. 

 litKjilianocrinns angidatns Conrad. Sil- 



