INVERTEBRATES. 293 



edges two larger secondary radial pieces, which also rest with 

 one side directly upon the first primary radials. Secondary 

 radials small, irregularly pentagonal, and bearing upon their 

 upper sloping sides the first brachial pieces, the outer two of 

 which in each ray, likewise have each one edge reposing upon 

 the lateral superior edge of the first primary radial. Anal 

 piece about one-third as wide as each first radial ; ovate in form, 

 the upper extremity being very narrow, the lateral margins con- 

 vex, and its base having an obtuse angle on each side, and one 

 in the middle. Arms (of which there are four to each ray, or 

 twenty in the entire series) simple from their origin, all rounded 

 on the outside, deeply grooved within, and each commencing 

 with a single series of large pieces, but soon passes into a double 

 alternating series of small pieces, bearing two ranges of tenta- 

 cles. Interradials apparently little larger than the first 

 brachial pieces, and probably wanting between the anal piece 

 and the first radials on each side. (Interbrachial appendages 

 unknown.) Height from base to summit of first radials, 0.16 

 inch; breadth at the top of first radials, 0.40 inch; breadth of 

 base, 0.24 inch; height of ditto, 0.16 inch; length of anal piece, 

 0.15 inch; breadth of ditto, 0.09 inch. 



Fig. 30. The smaller size and more graceful form of this species, 



— -j together with its much narrower, angular base, will at once 



1 distinguish it from the last. The sides of its body below 



the arms also differ in being more concave in outline, while 

 its anal piece is more contracted above and its arms more 

 slender. 



It is probably nearer P. pyrimidalis of Lyon and Casse- 

 Pterotocrinus chesterensis. day, but differs in being much smaller, and in having the 



(Nat. size.) . . 



Diagram showing the margins of its base angular instead of obtusely rounded. 

 and in two of the rays! I fc likewise differs in the proportions of its body below the 

 mary radials, secondary arms, the height and breadth being as 16 to 40, while the 



radials, and brachial and & « •'•77- • -1 r, 1 nr\ 



lower arm pieces. same measurements at jr. pyrimidalis are given as 18 to 80. 



Locality and position ; Same as last. 



