PLAXIPHORA. 327 



Plaxiphora terminalis CPE., MS. in Mus. Cuming. Chiton {Plaxi- 

 phora) terminalis E. A. SMITH, Voy. Erebus and Terror, Moll., p. 4, 

 t. 1, f. 13 (1874). Plaxiphora terminalis Smith, HUTTON, Man. N. 

 Z. Moll. 1880, p. 116 (reprinted from Smith.) 



Smith has described this species in detail, as follows: "Shell 

 elongately ovate, rather elevated, roundly angled along the top of 

 the valves, black or bluish-black, with a white wedge-shaped stripe 

 with a black one within it down the centre of the valves, forming a 

 continuous white stripe divided by the black one along the center of 

 the shell, in some specimens with a few short white dashes diverg- 

 ing from the radiating ridges. The intermediate valves mucronated, 

 bisected on each side by one raised radiating rib, the posterior mar- 

 gins sinuated and thickened by coarse concentric lamellae ; the 

 entire surface is covered with minute striate-wrinkling, those near 

 the ridge being coarser than the rest and radiating from it like the 

 webs from the shaft of a feather. The posterior terminal valve has 

 the mucro quite terminal. The anterior valve radiately eight-ribbed 

 (at times one or two additional minor ones are present) with diverging 

 oblique striations on each side of them. Interior of valves greenish- 

 blue ; valve lobes whitish, the sinus between them deep ; the hairs 

 or bristles on the mantle-margin are short, few and horny, those 

 arising from the nine pores being thicker than the rest. 



" Largest specimen (in a contracted state) 42 mill, long ; width of 

 valves, 20 mill. ; an average specimen, length 25 mill.; width 11 

 mill. 



New Zealand (Col. Bolton and Capt. Stokes.) 



" Terminalis " appears to be but a manscript name attached to 

 some specimens in the Cumingian collection. As I understand that 

 Dr. P. P. Carpenter is engaged on a work on Chitonidcel retain the 

 characteristic name he imposes. The central white stripe with the 

 black one within it appears to be very constant." 



Carpenter gave the varietal name zigzag, (in MS.) to specimens in 

 the Cuming collection (no. 31) having stronger sculpture, one more 

 anterior riblet, etc. It seems to be merely an individual variation. 



P. EXCURVATA Carpenter, n. sp. 



Shell elongated, elevated, the dorsal ridge rounded, valves angled 

 at the sides, obtusely beaked, the sutures indented. Irregularly 

 maculated with coppery green and black. 



Lateral areas defined by an obtuse curved rib ; toward the rib on 



