shown externally. a. a. a. Groves. b. b. Alleys. c. c. The lateral groves. d. The intermediate one. 3. Inside of the same shell. a. a. The dentated suture. b. The middle ridge marked out on each c. c. The alleys, with pores for the suckers. 4. Spines of Echinus cidaris. a. Muscular fibres inserted in the base of the spine, and surrounding the ball and 203-210 socket joint. b. The muscular capsule laid open, and the muscles attached to the base of the spine c. The origins of the muscles surrounding d. One of the tubercles. 5. One of the suckers of E. esculentus. a. The sucker; the pore in the centre is b. The stalk of the sucker. 6. The suture of a portion of the alleys at the Page FIG. 7. The suture of a portion of the lateral grove 8. Suture of the intermediate grove divided at 9. A circular space round the mouth, co- 10. Outside of one of the five pyramidal jaws, a. The jaw. b. The tooth. 11. Inside of ditto: a. the jaw, consisting in ternally of two triangular transversely 14. One of the spines of Echinus esculentus. PLATE III. B. CRINOIDEANS. FIG. 1. Pentacrinus Asteria 208-211 12 2. Portion of ditto, exhibiting the suckers on the under side of the fingers PLATE IV. TUNICARIES. FIG. 1. Cinthia Momus |