PLATE 3. 

 Eucidaris tribuloides (Lamarck). 



Fig. 1. Nassau, Bahamas. Diam. 48 mm. R. T. J. Coll., 741. X 7. Young plate from placogenous zone with develop- 

 ing spine In lower figure the plate is seen in side view and the spine is removed showing a low imperforate tubercle. 

 The spine is low, concave, saucer-shaped, as seen from the side and partially from lower view; the upper figure is 

 the same plate in face view with spine removed. Page 77. 



Fig. 2. Same specimen. X 7. The same plate in side view with the spine in pi Page 77. 



Phyllacanthus baculosa (Lamarck). 



Fig. 3. Mauritius. Diam. 44 mm. R. T. J. Coll., 752. X 2. Oculars V, I, IV insert, ail arrested variant. (Compare 



text-fig. 169, p. 149.) Pago 102. 



Fig. 4. Mauritius. Diam. 41 mm. R. T. J. Coll., 753. X 2. Oculars V, I, IV, II insert, III exsert, an arrested variant. 



Page 102. 

 Echinus microtuberculatus Blainville. 



Fig. 5. X about 160 (after Bury, 1895, Plate 7, fig. 34). oc., large oculars each with a four-pronged spine, and huge 

 tentacle, ten.; g, small genitals; a, b, two ambulacral plates each with a six-pronged spine below the ocular; i, prim- 

 ordial interambulacral plates each with a six-pronged spine. Pages 65, 87. 



Hypsiechinus coronatus Mortensen. 



Fig. 6. Very young (after Mortensen, 1903, Plate 7, fig. 6). Highly magnified. Oc., ocular plates; a, b, young ambu- 

 lacral plates of the corona; i, primordial interambulacral plates; P. A., primordial ambulacral plates; /, teeth. 



Page 65. 

 Schematic young echinoid. 



Fig. 7. Specimen in the protechinus stage, g, small genitals; oc., large oculars; a, b, young ambulacral plates of the 

 corona; i, young primordial interambulacral plates; P. A., primordial ambulacral plates; (. teeth. Pages 53, 90. 



Phormosoma placenta Wyville Thomson. 



Fig. 8. Young specimen. Diam. 3 mm. (niter Mortensen, 1907, p. 24). Highly magnified. The genitals meet in a ring, 



and as a consequence, the oculars must be exsart. (Compare adult, text-fig. 170, p. 149.) Page 110. 



Fig. 9. Young specimen. Diam. 3 mm. (adapted from Mortensen, 19C4, p. 54). Highly magnified. Only one row of 



primordial ambulacral plates on the peristome; the primordial interambulacral plates are in the basicoronal row. 



(Compare adult, text-fig. 43, p. 80.) Page 79. 



Fig. 10. Off Nevis, West Indies, 375 fathoms. Diam. 7 mm. (after A. Agassis, 1904, Plate 43, fig. 1). Two rows of 



ambulacral plates on the peristome. (Compare Bothriocidaris, Plate 1, fig. 1; also text-figs. 41, 43, p. 80.) Page 79 



Strongylocentrotus drbbachiensis (O. F. Muller). 



Fig. 11. Very young specimen. Diam. 1.2 mm. (after Lov6n, 1892, Plate 4, fig. 25). X about 50. Lantern inclined, 

 interpyramidal muscles long, ten primordial ambulacral plates only on the peristome, primordial interambulacral 

 plates in basicoronal row, ambulacral plates of corona high, simple. (Compare text-figs. 49, 50, p. 80 ) Page 65. 



Phyllacanthus baculosa (Lamarck). 



Fig. 12. Mauritius. Diam. 45 mm. R. T. J. Coll., 901. Ambulacrum II, showing spinules on the interior of ambulacral 

 plates; c, from the ambitus, X 5.5, a single spinule over each inner.pore; d, enlargement of same, X 10.3; b, from 

 the base of the corona, X 5.5; another set of blunter spinules appears between the pores and the middle of the area. 

 (Compare Plate 24, fig. 6.) Ventrally, these inner spinules are fused into, a continuous ridge (compare text-fig 224, 

 p. 193). a, enlargement of two plates, X 10.3, showing the two sets of spinules. Page 61. 



Eucidaris tribuloides (Lamarck). 



Fig. 13. Jamaica. Diam. 43 mm. R. T. J. Coll. Ambulacrum II, showing spinules on the interior of ambulacral plates. 

 X 5.3, and one plate, X 10.6. There are three spinules over the inner pore of each plate. Page 61. 



Echinus magellanicus Philippi. 



Fig. 14. Patagonia. Diam. 3 mm. R. T. J. Coll., 894. X 19. Oculars all ex.sert, no genital pores exist, and only one 

 madreporic pore; the suranal plate fills the periproct. (Compare adult, text-fig. 165, p. 149.) Pages 119, 176. 



Collyrites acuta Desor. 



Fig. 15. After Lov6n, 1874, Plate 6, fig. 55. In the basicoronal row there are ten primordial ambulacral plates: the la, 

 Ila, III') IVa, Vb are larger each with two pairs of pores, the Ib, lib. Ilia, I\'b, Va are smaller each with one pair 

 of pores also five primordial interambulacral plates are in the basicoronal row, succeeded in the second row by two 

 plates in'eachjarea. Page 56. 



