198 



ECHINODEKMATA— PELMATOZOA 



PHYLUM IV 



and elevated ; anus eccentric. All bifurcations beyond costals given off from 

 every alternate brachial. Lovver Carboniferous (Lower and Upper Burlington) ; 

 North America. 



Strotocrinus M. and W. Interbrachials not connecting with tegmen. 



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Fio. 299. 



A, Cactocrinus proboscidialis (Hall). Lower Carboniferous ; Burlington, Iowa. Calyx witli fractured 

 tegmen, showing the subtegminal ambulacral skeleton, and the convoluted digestive organ. B, Enlarged 

 portion of the ambulacral skeleton, C, Natural cast of tegmen of Phy^ietocrinus, with impressions of food- 

 grooves (a), condncting from the arms to the mouth (o) ; an, Anus. D, Diagraui of Äctinorrinus (after W. 

 and Sp.). 



Calyx not lobed ; rays bifurcating on alternate brachials from distichals up, 

 and extended into a broad, flanging rim, as in TeMocrinus, but more 

 pronounced. Arms very numerous and slender. Tegmen low, sometimes flat 

 or concave, composed of innumerable small pieces ; anus eccentric. Lower 

 Carboniferous (Upper Burlington) ; North America. 



Family 9. Platycrinidae Roemer. 



Monocydic. Brachials and interbrachials usually but slightly represented in the 

 dorsal citp : the lower brachials taking more or less the form of arm plates, but being 

 strongly connected^ either with the solid tegmen by modified covering plates and strong 

 interambulacrals, or with the cup by large interbrachials which are usually more or 

 less interambulacral in position. Radiols in contact all around, there being no 

 special anal plate. Basais forming a pentagon ; three, unequal, and frequenÜy 

 anchylosed. Silurian to Carboniferous. 



