ON SOME PELMATOZOA FROM CHAZY LIMESTONE OF NEW YORK II5 



the older hydrospires and the marked widening of the ambula- 

 crum toward the same area in this species (and in Asteroblastus 

 and related forms) is to me indicative not alone of the required 

 slight increase of size of the food groove but also of the increase 

 of the functions of respiration and reproduction. 



At certain points in grinding down the section shown in fig- 

 ure 2 there was visible a small rather square figure outlined by 

 carbon particles and lying directly under the inner ends of the 

 adambulacrals. This suggests a radial water canal which may 

 have been connected with the hydrospires through side branches. 

 If this additional structure existed the similarity between this 

 ambulacrum and that of an asteroid would be extraordinary, 

 the hydrospires being comparable to ampullae and the lining 

 of the brachiolar cavities to podia. 



Anal piece. The wing plates radiate from a high central star- 

 shaped plate apparently formed from five consolidated orals or 

 from five upper or orad portions of the deltoids as shown in 

 figures of Asteroblastus where the food grooves are made to 

 pass over the outer edges of a starlike central portion which 

 resembles in a very remarkable manner the central piece of 

 Blastoidocrinus. In the latter species however the food grooves 

 lie on a horizon but little above the bases of the brachioles 

 or at a depth below this apical piece equal to the sum of the 

 extreme depth of a wing plate and the hight of the massive 

 covering plates. A reference to plate 2 will show how far down 

 this must be. The apical piece stands in the same relation to 

 the covering plates of the peristome as the wing plates do to the 

 covering pieces of the food groove. There is plenty of room 

 under this piece for a series of covering plates as in Nucleocrinus 

 but with the anus thrust through them and by a bend above 

 them opening laterally at a surface flush with the grooved side 

 of the plate and just back of the peculiar brachiole of the anal 

 interradius. Thus the apical piece might better be considered 

 as formed of fused anals than of fused orals. We may note 

 that it is possible that the anus had no external opening. If 

 echinodermal respiration may be in part effected by water enter- 

 ing the alimentary canal by either mouth or anus (as in the 

 " respiratory trees " of holothurians, the " accessory intestine " 

 of echinoids and the " ventral sac " of crinoids) we may possibly 

 have here a somewhat similar condition of things in which there 

 is a flow from the rectum over the covering plates of the peri- 

 stome and swept away through the older and larger hydrospires. 



