ACTINOCRINID^. 619 



but somewhat decreasing in widtli ; moderately flattened on tlie bacls, but 

 without surface markings; the sides slightly dentate. The spines of the 

 pinnules rather short. Interbrachials : 1, 2, 2, 1, the first a little larger 

 than the costals. The anal plate, which is generally narrower than the 

 radials, supports 2, 3, 2, and 1 piece, the latter followed by a narrow elon- 

 gate plate, placed between the arm-bearing brachials. Interdistichal spaces 

 deeply depressed, and the centre occupied by a small, nodose plate. Ven- 

 tral disk very high, the interambulacral spaces slightly grooved toward the 

 arm regions. Plates more or less tumid, iri'egular in form and size. Orals 

 indeterminable, and possibly unrepresented. Covering pieces of first and 

 second orders represented by single plates ; the succeeding orders by two 

 rows of small alternate pieces, which take part in the tegmen. Anal tube 

 strong, constructed of similar plates to those of the ventral disk, but some- 

 what smaller. Column apparently small ; axial canal large for the genus 

 and quinquelobate. 



Horhon and Locality. — Same as last. 



Tijpe in the (Worthen) Illinois State collection. 



Cactocrinus coelatus var. spinotentaculus Hall. 

 Plate LIX. Fig. 10. ■ 



I860. Acfinocrimis spinotentaculus — Hall; Suppl. Geol. Kep. Iowa, p. 86; N. T, State Mus. Nat. Hist., 



Bull. I. (1872), Plate %A, Egs. 13 to 17. 

 1885. Actinocri?ius spinotentaadus — W. and Sp. ; Revision Palieocr., Part III., p. 112. 



Agreeing with C. coelatus in the number of arms, the arrangement of the 

 plates, and their style of ornamentation ; but departing from it in the form 

 and proportions of the calyx, which expands abruptly from the distichals, 

 and is at the arm bases almost as wide as high. Adinocnms spinotenta- 

 culus is in our opinion only an extravagant form of Cactocrinus coelatus, in 

 which some of the arm joints, which in the latter are free, were incorpo- 

 rated into the calyx ; and this, together with a slight increase in the thick- 

 ness of the arms, fully explains the modifications above mentioned. 



Horizon and Locality. — Same as last. 



Type in the University Museum, Gottingen, Germany. 



