LOO V. A. BATHKR, CKINOIDEA OF GOTLAND. 



Sub-order: inadunata vicyclica. 



[nadunata with infrabasals. 



The genera of Inadunata that have infrabasals in the dorsal eup appear to form a 

 fairly homogeneous group. None of theni present that deviation from pentamerous sym- 

 metry in the cup-plates that we have seen to be of such common occurrence among 

 Monocyclic genera. Only in the right posterior radius are there ever seen traces of that 

 horizontal bisection of certain radials that is so characteristic of the Heterocrinida;, the 

 Calceocrinidae and other Monocyclica. 



The classitication of these forms has been very fully discussed in »British Fossil 

 Crinoids, II, The Classification of the Inadunata Fistulata.» 1 ) I have there endeavoured 

 to show that they may most naturally be divided among three main families, — Dendro- 

 crinidae, Decadocrinida' and Cyathocrinidse, although a few genera that are not easily 

 arranged with the rest neeessitate the temporary maintenance of the families Caraboerinidaj 

 and Euspirocrinidas. Within these three main families the genera may further be sepa- 

 rated under the head of series, which mark off the different stages of the evolution of 

 the families. 



The lapse of nearly three years, during which my knowledge of the Inadunata has 

 greatly iuereased, has brought nothing to light to disturb the main lines of that classi- 

 fication; consequently that will be the one adopted in the present paper. 



Dendrocrinid^e. 



Inadunata Dicyclica, with K alone, or with anal x alone, or with R' and anal x, 

 or with a radianal, anal x and one plate of the tube, in the anal area of the dorsal cup; 

 with broad radial facet; with diehotomous arms, that may or may not develope pinnules; 

 with a tegmen eomposed of small plates, and with a ventral tube that is usually long 

 and transversely rlattened. 



This Family was proposed 2 ) to include a large number of genera hitherto distributed 

 among the Cyathocrinidae and Poteriocrinidse of authors. The family is distinguished from 

 the Decadocrinidse by the continuous dichotomy instead of the single bifureation of its 

 arms; at the same t i me, since the Decadoerinida 1 are lineally descended from certain Den- 

 drocrinids, there are naturally forms that bridge the gap. From the Cyathocrinidae it is 

 distinguished l>v the fäet that the anal area is never without soine plate, by the wide, 

 slightly specialised radial facet, and by the more delicate tegmen. It differs from the 

 Carabocrinidae in that no plate ever descends from the anal area to touch the infrabasal 

 circlet; and from the Euspirocrinidse in the more delicate tegmen, and in the anal tube. 



') Ann. :\hi£. Nat. Hist., ser. 6, vol. V, pp. 310 334 and 373 — 388: 1890. 

 -i Brit. 1'uss. Crin. IL- Ann. Mag. Nat. Hist., ser. B, vol. V. p. 383. 



