MUSEUM OF COMPARATIVE ZOOLOGY. 2G5 



Naples. 10-11, showing a stump covered by skin, and another with the skin 

 partly torn off: Naples. 12-13, stumps from lower interbrachial space of a 

 young, having a disk of 2.5 mm. The scales of the disk are then visible, and 

 Fig. 13 shows how one stump stands on each scale : Naples. 14, a short spine 

 from the interbrachial space below : Algeria. 



15-20, (J. lusltanica, Naples; 16- IS being from the young; 15, 19, 20, from 

 an adult ; the last (20) is a very rare spine. 21 -29, N. W. coast of France ; of 

 these 22 is the common form ; the rest are more or less rare ; 28 is found near the 

 edge of the disk. 



30-35, O. pcntaphyllum, Isle of Wight ; of these 30-33 are thelbharacteristic 

 grains and stumps of the centre of the disk ; 34, 35, are its thick columnar spines ; 

 36, a disk spine : Madeira ? 



O. fragilis. 41, stump from a young, with a disk of 5.5 mm. 37, 40, 42, two 

 stumps and a spine from a disk 7 mm. in diameter. 44, an elongated stump from 

 the edge of a disk 9 mm. in diameter. 38, 39, stumps from a large specimen 

 (disk 16 mm.) ; 39 is rare : Denmark. 43, rough grain from centre of disk ; large 

 specimen : Sweden. 



O. qvdnquemaculata. 46, 47, stump and articulated spine from a young, with a 

 disk of 3.5 mm. : Naples. 52, 53, short and elongated stumps from a disk 

 7.5 mm. in diameter ; the latter from the edge. 51, articulated spine from a large 

 specimen. 45, irregular, thickened spine from an adult. 48, 49, 50, short 

 stumps from the centre of a large disk. 54, an elongated stump from the edge of 

 the same. 55, a large stump like 49, much elongated : Spezia. 



PLATE III. 



Growth of Spines, Hooks, and Stumps. 



Ojihiofhrix alopcciirus Mull. & Trosch. Ophiothrix rudis sp. nov. Ophiothrix 

 stclligcra sp. nov. Ophiothrix pusilla sp. nov. 



Fig. 1. The fluted form of the long spines which cover the upper surface of the 

 disk, except the radial shields, in O. alopecurus. These usually are more slender, 

 with smaller side thorns and only slight appearance of fluting; a ] a . 



Figs. 2, 3. Minute spines, simple and forked, which sometimes are found sparsely 

 on the radial shields ; *p-. 



Fig. 4. A young arm-spine from near tip of arm, showing a central shaft with 

 thorns forming on either side, and the holes, along the two lines of juncture, not 

 yet filled up ; *£. 



Fig. 5. A similar spine with the side thorns broken off to show more distinctly 

 the central shaft ; 7 i°. 



Fig. 6. Tip of a similar spine more magnified, to show the holes along the lines 

 of juncture, holes of growth; 1: j Q . 



Fig 7. Fragment of a very young spine much magnified, to show the soldering 

 of a thorn with the central shaft, and the holes of growth. 



