26 AMPHINEURA. [Poly placophora. 



aa. Anterior valve having 5 radiating ribs, its lower margin 5-lobed ; 



girdle with 18 small pore-tufts. 

 b. Girdle leathery, naked except tufts . . . . . . violaceus. 



bb. Girdle covered with white spic\iles, especially at the 



margin . . . . . . . . . . . . rubiginosus. 



bbb. Girdle leathery ; latero-pleural areas with elongated 



granules . . . . . . . . . . Marice. 



Sect. 1. ACANTHOCHITES, S.S. 



Acanthochetes, Gray, P.Z.S., 1847, 109. Acanthochiton, Herrmansen, Indie. 

 Gen. Mai. Prim., i, 2. Acanthochistes, Costa, Faun. Reg. Nap., 2. 

 Phakettopleura, Guilding, Zool. Journ., v, 28. Stectoplax, Carpenter, in 

 Ball, Proc. U.S. Nat. Mus., 1881, 284, 288, 289, 291. 



Valves partly covered, the anterior lacking radiating ribs ; the 

 posterior valve having the insertion plate with a single slit on each 

 postero-lateral edge, and a wide toothless sinus in the middle behind. 

 Girdle with large dense tufts of glistening spicules. (Pilsbry.) 



Type : Chiton fascicularis, L. 



In this, the typical section, the tail valve has been further differen- 

 tiated from the primitive type than in the other sections. The hairs 

 of the girdle, and especially the tufts, are more exuberantly developed 

 than in any other group of Chitons. (Pilsbry.) 



1. Acanthochites zelandicus, Quoy and Gaimard, 1835. Plate 2, 

 fig. 9 ; Plate -i, fig. 1. 



Chiton zelandicus, Q. & G., Voy. Astrol., iii, 400, pi. 73, f. 5-8. Acantlm- 

 chites zelandicus, Man. Conch. (1), xv, 16, pi. 14, f. 9, 10 ; P. Mai. S., ii, 

 192. Acanthochceies Hookeri, Gray, in Dieff. N.Z., ii, 262. Acantho- 

 chites spiculosiis astriger. Reeve : Wissel. Zool. Jahrb., Syst., xx, 612, 

 pi. 21, f. 25 ; pi. 23, f. 26, 27 (anatomy) ; not of Reeve. A. bisulcatits, 

 Pilsbry : Wissel, t.c., 614, pi. 23, f. 28, 29 (anatomy), not of Pilsbry. 



Shell elongated, moderately elevated, hardly carinated ; greenish, 

 grey, or yellowish. Anterior valve finely granulose, apex smooth, some- 

 times carinated and beaked. Intermediate valves more or less distinctly 

 beaked ; latero-pleural areas covered with closely crowded, ovate, 

 flattened granules ; dorsal areas narrowly triangular, closely and finely 

 striated longitudinally. Posterior valve with the tegmentum small, 

 transversely oval, decidedly wider than long. Girdle rather narrow, 

 greenish or yellowish, covered with short spicules, having a. marginal 

 fringe of longer spicules, and 18 tufts of light-blue or white bristles. 

 Colour brown, greenish, grey, or yellowish, sometimes dotted with 

 brown, some valves with a brown or black line at the summit, margined 

 with white. Interior dark blue-green or dark grey ; anterior valve 

 with 5 not deep slits, teeth broad and sharp ; intermediate valves 

 with a small posterior slit ; posterior valve with the post-median 

 sinus shallow, insertion plate biangular behind, 1 small slit on each 

 side, the edge between them often minutely crenulated ; sinus wide, 



