Fig. 02. Chjpeastcr reticulafus L. The half-pyramid .5 h seen from the am- 

 bulacral side, cut vertically iu tlie directiou of the line B, tig. 58, 

 and partly fractured so as to lay opeu the fossa, the alveolar cavity 

 aud the dental groove. The tooth is represented as if transparent. 



Fig. 03. The same, the auricle heiug renioved, to show the muscles, X the 

 attachment line of the m. re. 1. 



Fig. 54. Part of the same seen from the interradial side, tlie pyramid being 

 removed. 



Fig. 55. The auricular hranches V b and I a seen from ahove; X as in fig. 53. 



Fig. 56. Vertical sectiou aloug the line A fig. 52, seen interradially from the 

 interiör, in the direction of the arrow. 



Fig. 57. The pyramid 4 from its upper side, denuded. 



Fig. 58. The pyramid 5 from its under side. 



Fig. 59. The pyramid 5 a, lateral view of the inter-pyramidal surface of 

 the wing. 



Fig. tio. The half-pyramid 4 a, from the side of the symphysis; the tooth 

 drawu as if transparent. 



Fig. Gl. The mouth with the ends of the five teeth. 



Fig. G2. A rotula, side view. 



Fig. 63. Echinometra Lncnnter L. A pyramid with the epiphysis seen 

 laterally. 



Fig. 64. The same from the external side. 



