ON SOME PELMATOZOA FROM CHAZY LIMESTONE OF NEW YORK II3 



The upper surfaces of some of these plates may be seen in plate 

 I, upper figure, and an impression of these surfaces in plate 6, 

 figures k and 1. 



Wing plates. Along the center of each ambulacrum and 

 between the upper portions of the two rows of brachioles but 

 rising a little above their closed tips, there is a linear series of 

 three somewhat razor-shaped plates with their broad and slightly 

 concave backs uppermost. I have called these wing plates and 

 have outlined the exposed surface of two rows of them in fig- 

 ure i of the text. In plate 6 at a, b, c and d, are different 

 views of four first wing plates ; b and c show outer surfaces 

 [the proximal end of c is probably the lower end of the figure]. 

 These plates lie nearest the anal piece and are the shortest. 

 At e, f, g and h, are different views of four second wing plates. 

 At i, j and k are different views of some third wing plates ; 

 k shows the impression of the tops of the covering plates which 

 are more clearly shown at 1, which is an outline drawing of the 

 same face of the specimen. These last become longer than the 

 second plates and usually terminate the row. In the specimen 

 figured on plates I, 2 and 3, the knife-bladelike points of these 

 curve down to and touch the smallest end brachioles of the 

 ambulacrum. 



Figures b, f and j show surface ornamentation due to addi- 

 tions through growth. The first wing plate, b, was the first 

 of its series formed and additions were made principally at its 

 sides, its base, and its distal end. The original small second 

 wing plate may still be clearly seen as the innermost V in fig- 

 ure f, and six additional periods of growth have left the arms 

 for six additional V's or rounded ridges. This plate seems to 

 have attained its full length at the end of the third of these 

 seasons and thereafter only increased its hight and width. Fig- 

 ure j shows the same process of extension of the third wing- 

 plate and older specimens may have added a small fourth. Fig- 

 ure k seems to be a third wing plate that did not terminate the 

 row. The hollow or grooved upper surface, shown clearly at d, 

 was produced by an upward extension of the edges of the plates 

 to keep just in advance of the extending tips of the brachioles. 

 Figures c and g show a labyrinthine surface ornamentation much 

 like that found on the proximal third of some radials. Traces 

 of the same may be seen at b. In c the growth lines are very 

 nearly obliterated, in g one does not detect them. 



