REPOKT ON THE POLYPLACOPHOEA. 17 



pheral portion of the terminal valves and lateral areas is marked by slight concentric lines 

 of growth. 



Colour. — White, with a few irregular dark flecks on the sides. 



Girdle. — With delicate, imbricate, coarsely striated scales.. 



Specimens in the Zoological Museum of the University of Cambridge are very similar, 

 they are of a creamy-yellow colour, very slightly tinged with green, the lateral areas are 

 moderately elevated. 



Ischnochiton longicymba (Blainville). 



Chiton longicymba, Blainville, Diet, des Sci. Nat., 1825, vol. xxxvi. p. 542 ; Quoy and Gaimard, 



Voyage de 1' Astrolabe, Zool., 1834, vol. iii. p. 390, Atlas, pi. lxxiv. figs. 



1-18 ; Deshayes in Lamarck's Hist. Nat. Anim. s. vert., 1836, vol. vii. p. 512 ; 



Sowerby, Conch. Illustr., 1841, No. 45, pi. clx. fig. 67 (vars.); Eeeve, Conch. 



Icon., 1847, pi. xxiv. fig. 163. 

 Lepidopleurus longicymba, Angas, Proc. Zool. Soc. Lond., 1865, p. 187, and 1867, p. 222. 

 Ischnochiton longicymba, Dall, Proc. U.S. Nat. Mus., 1878, pp. 78, 113. 



Habitat. — Port Jackson. 6 to 15 fathoms. 



Australia and New Zealand. 



I have identified as this species three specimens obtained by the Expedition from Port 

 Jackson. The shell is elongated, having a rounded angle, and with the lateral areas but 

 slightly raised. The whole of the central areas are delicately shagreened ; the lateral 

 areas and terminal valves with very fine interrupted and often bifurcated ridges. The 

 whole shell has a decidedly smooth appearance. One specimen is of a pale creamy green 

 colour and another pale pink, both with a few dark spots on the central areas ; the third 

 is white, with a black band all round the edge, and with usually paired black marks on 

 several of the valves on each side of the jugum, resembling in some respects Quoy and 

 Gaimard's fig. 14. The girdle is indistinctly banded. 



Ischnochiton fruticosus (Gould). 



Chiton fruticosus, Gould, Proc. Boston Soc. Nat. Hist., 1846, vol. ii. p. 142; U.S. Explor. Exped. 

 (Wilkes), 1852, vol. xii. p. 319 ; Otia, 1862, p. 4, and Kectifications, p. 242. 

 ,, divergens, Eeeve, Conch. Icon., 1847, pi. viii. fig. 44. 

 Lepidopleurus proteus (1), Angas (? of Eeeve), Proc. Zool. Soc. Lond., 1867, p. 222. 



Habitat. — Port Jackson. 6 to 15 fathoms. 



New South Wales (Gould) ; New Holland (Jukes-Reeve) ; Port Jackson (Angas). 



This is a very variable form, not only in colour but also in sculpture. In order to 

 define the limits of this and allied species a large number of specimens is necessary. The 

 following species form a series, appearing to pass more or less into each other, or at all 

 events to be closely allied : — Ischnochiton longicymba, Blainville ; Ischnochiton fruticosus, 



(zool. chall. exp. — part xxiii. — 1886.) Uu 3 



