41. Echinoderms exhibit secondary radial symmetry in portions of their body at some stage of life.42. The uppermost portion is the only one homologous with the nervous systems of other echinoderms . 43. The relationships among ophiuroids and all other echinoderms provide an enduring problem in invertebrate evolution. 44. Which is the most authoritative source on echinoderms , and what figure does it give? 45. More puzzling is the reason for the fivefold ( pentaradiate ) symmetry of the echinoderms . 46. This sea was home to life like bivalves, echinoderms , foraminiferans, and gastropods. 47. This is the kind of situation you get into when you travel with an echinoderm lover. 48. They are often associated with echinoderms . 49. They are spiny, hard echinoderms . 50. Echinoderms are marine animals, widespread in all oceans, but not found in fresh water.
