THE CRINOIDEA 



127 



simulating that of primitive orals (e.g. Gissocrinus, Fig. XLL, Crotalo- 

 crinus, Fig. XCII. ; cf . Eublastoidea). Other ambulacrals, especially 



FIG. XXXVIII. 



Tegmen of Euspirocrinus spiralis, showing four cordi- 

 form deltoids or orals, and a madreporite, with ambu- 

 lacrals overlying their apposed edges. In the pos- 

 terior interradius is the base of the broken oft' anal 

 tube. (From Bather, 1893.) x 3. 



Fio. XXXIX. 



Tegmen of Cyathocrinus. 1,.C. 

 plamis with ambulacrals and intVr- 

 ambulacrals removed, exposing 

 apposed edges of orals (A) and 

 madreporite (M ). 1, C. mnmmillaris 

 with ambulacrals (r/>) and interam- 

 bulacrals (io) almost entirely cover- 

 ing orals (A) and peristome. (From 

 Bather, 1892.) x 2. 



axillary Amb, increase in size, and form prominent bosses on the 

 tegmen, called " radial dome-plates " (Fig. XLII.) ; the effect of 

 this is enhanced by the sinking of the other ambulacrals (e.g. 



Amb> 



\eoeriiati /i>7ss, to exemplify the simplest 

 tyjH) of Cawerate tegmen. 1, from 1. post, radius; 

 2, from above. As, anus ; B, basals ; br, opening 

 for food -groove and underlying canals; ib, large 

 interbrachials (suborals, Jaekel). Other letters as 

 usual. (After Joh. Mttller, 1855.) x 2. 



FIG. XLL 



Tegmen of Gissocriniig arthriticus, 

 showing ambulacrals (Amb) passing 

 down arms and over apposed orals 

 (0),and becoming enlarged over peri- 

 stome. Post. O remains as a folded 

 madreporite ; t, anal tube. Other 

 letters as usual. (From Brit. Mus. 

 46457.) X 3. 



Actinocrinidae). These two facts suggest that the proximal dome- 

 plates of Camerata, regarded as orals by Wachsmuth & Springer, 

 and so quoted under head (3), may after all be modified ambulacrals. 



