CLASS III CRINOIDEA 207 



Order 3. INADUNATA Wachsmuth and Springer. 



Crinoidea in which the arms are free ahove the radials ; dorsal cup limited to 

 radials, hasals, in/rabasals when present, and anal plates ; no interradials oi' inier- 

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

 in the cup. All plates of the cup united hy dose suture. Mouth suh-tegminal. 



Suborder 1. LARVIFORMIA Wachsmuth and Springer. 



(Haplocrinacea Neumayr ; Larvata Jaekel pars). 



Monocyclic {except Cupressocrinus). Calyx consisting only of hasals {with or 

 without infrahasals), radials, and orals, without anal plates, and usually without 

 visible ambulacra. All plates immovably united hy dose suture. Arms non- 

 pinnulate, simple and uniserial {exception, the doubtful Stephamcrinus). Silurian 

 to Carbon iferous. 



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 such as 

 may belong to an arm-like anal tu^be. They are usually small, one genus, Allagecrinus, 

 alraost microscopic. Similar minute fornis may yet be found in the pre-Silurian forniations, 

 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 hasals, five radials, 

 and five orals, with ambulacra. Radials deeply forked ; the pi'ongs formed hy 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 m'als, surrounding a 

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

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

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

 process. Arms with one short biserial trunJc to 

 the ray, giving off slender biserial, non-pinnulate 

 side arms from the outer Shoulder of each brachial. 

 Ordovician and Silurian. 



Stephamcrinus 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 fio. 308. 



pointed out by Wachsmuth and Springer ^^.^^i;:;^;-^^^^^^^ 



makes it Unquestionably a CrinOld, althOUgh of calyx, natural size ; b, Snmmit aspect, 

 -, r i , • , V.;^!« ;<- enlarsred ; nroiecting upper ends of the 



not normal f or the present group, m wtiicti it ^^^^^^^ ^roken away (after Haii). 

 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. 



