CBINOIDEA. 293 



Crinoids in which they differ markedly from Asteroids, though 

 not so far as is known from other classes.* 



Order 1. LABVIFORMIA (Inadunata larviformia Wachsm.) 



The calyx-cover consists entirely or almost entirely of five triangular 

 oral plates which are applied together so as to form a pyramid and cover 

 the ambulacral grooves of the disc as well as the mouth, f The calyx is 

 monocyclic and consists of basals and radials only except in Cupresso- 

 crinidae and Stephanocrinidae, there being no interradial plates except 

 in the anal interradius. The anal interradius is frequently unlike the 

 other interradii. The plates are immovably connected by smooth 

 sutural surfaces. The arms are weakf and entirely free. The large orals 

 and simply constructed calyx are characteristic of larvae of living Crinoids. 

 Upper Cambrian to Carboniferous. 



Fam. 1. Haplocrinidae. Calyx small, irregular, with five unbranched 

 arms. Some of the radials are composed of two pieces (Fig. 199). Anus 

 is in the posterior oral. Haplocrinus Steininger (Fig. 

 199), Devonian. 



Fam. 2. Allagecrinidae. Calyx small ; basals and 

 radials 5. Oral plates triangular. Allagecrinus Eth. 

 and Carp. 



Fam. 3. Pisocrinidae. Pisocrinus de Kon. Tria- 

 crinus Miinst. 



Fam. 4. Symbathocrinidae. Symbathocrinus Phillips, 

 Phimocrinus Schultze, Stylocrinus Sandb., Stortingo- p IG 199. Haplo- 

 crinus Schultze, Lageniocrimis de Kon. crinus mesptti- 



for mis (from 



Fam. 5. Cupressocnnidae. Calyx pentamerally Delage and H6rou- 



symmetrical, 5 basals, 5 radials, no interradials. The ard, after W. 

 basals surround a pentagonal centro-dorsal plate ( ? top ^nal side, 

 segment of stalk). 5 broad and thick arms, which 

 are traversed by a nerve canal. Cupressocrinus Goldfuss, Devonian. 



Farn. 6. Stephanocrinidae. Calyx composed of 3 high basals, 5 deeply 

 forked radials, and 5 small interradials ; with branching arms (each arm- 

 joint gives off side arms which are non-pinnulate). U. Cambrian, Silurian. 

 Stephanocrinus Conrad. 



Order 2. FISTULATA (Inadunata Fistulata W. and S.) 

 Calyx covered with thin plates which easily fall apart from one another 

 and may be prolonged in the anal interradius into a usually high balloon- 

 shaped, or short conical tube. The ambulacral furrows are covered by 

 alternating covering pieces but are not subtegminal. The mouth is 

 eccentric and sometimes subtegminal (see p. 280). Basals and radials 

 of the calyx immovable, connected by simple suture. Arms free, no 

 brachial included in the calyx, uni- or bi-serial, usually branched, 

 the segments connected by simple sutures, with or without pinnules. 

 Interradial anal plates may be present in the anal interradius, one of them 



* It is somewhat surprising, having regard to their early inequality in 

 Asteroids, that in Holothurians and Echinoids, in which the ambulacral 

 surface of the adult so much exceeds in area the antambulacral, the right 

 and left posterior coeloms should remain approximately equal in size in 

 the larva. 



f Exception Cupressocrinidae. 



