2G8 BULLETIN OF THE 



Fig. 32. Second arm-spine ; 1 i h -. 



Fig. 33. Ophiothrix fumaria (from the original in the Garden of Plants). A 

 portion of upper surface of disk, with some upper arm-plates. On either side of 



the points of the radial shields appear the upper corners of the genital scales ; \. 



Fig. 34. Under arm-plates, with tentacle-scales. 



Fig. 35. Arm-spines, near base of arm ; f . 



Fig. 36. A disk-stump on its scale, much magnified. 



PLATE V. 



Formation of Arm-spines, Arm-plates, and Supplementary Pieces. 



Pcdinura marmorata sp. nov. ; Hemieuryale pustulata v. Mart. ; Ophioplocus 

 Esmarki sp. nov. ; Ophiura squamosissima Lym. ; Ophiura cincrca Lym. ; 

 Ophiopholis aculcata Mull. & Trosch. ; Ophioncrcis dicbia Lym. 



Fig. 1. Pectinura marmorata. The tip of an arm undergoing repair. The 

 point is only a tube of calcareous network, covered by the secreting membrane. 

 Farther in, this tube is widened and cut transversely by furrows into joints, which 

 have lobes at their outer edge ; and these lobes grow more sharp and rounded, and 

 finally become the lowermost arm-spine, p. There are no under arm-plates at this 

 stage of growth ; i 1 Q . 



Fig. 2. The same from above. Almost the entire surface is occupied by the 

 side arm-plates, at whose central point of juncture appear little collections of 

 granules, j, which are to be separated later as upper arm-plates ; ^-. 



Fig. 3. The same seen from the side. One joint has two partly formed arm- 

 spines, p, and the next joints have one each ; ^p. 



Fig. 4. The broken arm under repair, showing the old portion, and eighteen 

 new joints ; of which the rast five are represented in Figs. 1, 2, 3 ; -"". 



Figs. 5, 6, 7. Two joints, close to the disk, seen from below, from above, and 

 from the side, to compare the perfect plates and spines with the young ; \ n -. 



Fig. 8. Hemieuryale pustulata. Tip of the arm, magnified, showing the tubu- 

 lar point, the side arm-plate, i, and the young upper arm-plate, j. 



Fig. 9. A joint near the tip, seen from above. j>, arm-spine ; i, side arm-plate ; 

 j, upper arm-plate ; k, supplementary piece. 



Fig. 10. Joint farther inward. i, side arm-plate ; j, upper arm-plate ; I; sup- 

 plementary piece, in addition to which there are now numerous others, smaller. 



Fig. 11. Joint about one third out on the arm. k, the great supplementary 

 piece, which now is larger than the side arm-plate, i, and forms the little cushion 

 characteristic of the genus. The upper arm-plate can no longer be distinguished 

 among the numerous irregular supplementary pieces. This is an instance of great 

 changes in the relative importance of parts in the process of growth. 



Fig. 12. Ophioplocus Esmarki. Tip of arm showing the very short tubular 

 point, followed by a joint which has a small upper arm-plate. The corresponding 

 plate of the next joint has a longitudinal furrow ; the same is fairly separated in 



