PLAXIPHORA. 319 



bly's name, evidently by inadvertence. 



The figures represent C. hahni Rochebr., which I believe to be 

 identical. It is thus described : 



Chcetopleura hahni [pi. 67, figs. 37, 38]. Shell broad-ovate, flat- 

 tened, obtusely carinated, violaceous-bluish, with spots and lines of 

 brown irregularly distributed. Anterior valve rounded, with 10 

 radiating ribs. Posterior valve very small, elliptical, feebly beaked. 

 Lateral areas of the median valves narrow, bounded by a beaded 

 rib ; central areas covered with deep concentric stride, and very 

 minutely striated transversely. Girdle wide, brown, covered with 

 tawny hairs. Length 48, breadth 35 mill. (Rochebr une.') 



P. BIRAMOSA Quoy & Gaimard. PI. 68, figs. 51-54. 



Animal ovoid, elongated, flattened, valves very transverse, little 

 elevated, forming a low arch, not carinated ; striated transversely in 

 front. White or green with a circle of red-brown on each valve. 

 The anterior valve has 9 teeth on its edge, the posterior valve none. 

 The sutural laminse are not wide, and are separated only by a very 

 obtuse sinus. The insertion plates are slit at the sides at usual. Inte- 

 rior dull white. 



Girdle nude, vivid red-brown, having two spaced series of rough, 

 sparse and bifurcating hairs, the inner series contiguous to the 

 valves, the other near the periphery of the girdle, which is also 

 hairy. (Q. & .) 



Length 45, breadth 31 mill. 



Chiton biramosus Q. & G., Voy. de 1'Astrol. Zool. iii, p. 378, 

 t. 74, f. 12-16. Plaxiphora biramosa Q. & G., HUTTON, Man. N. Z. 

 Moll. 1880, p. 116 (translation of Quoy's diagnosis). Acanthochcetes 

 biramosus HUTTON, Trans. N. Z. Inst. iv, p. 181 (incorrect descrip- 

 tion, from Deshayes). Placiphora super ba CPR. MS. 



The external form is noticeably different behind in the two 

 individuals which we possess ; but the red color of this species and 

 its two series of bifurcating spines will readily distinguish it. ( Q. 

 & .) 



I believe the form which Carpenter described in MS. as P. superba, 

 is the same as Quoy and Gaimard's C. biramosus. Carpenter's 

 description is as follows : 



P. superba (pi. 68, figs. 55-61). Shell large, oval, elevated, the 

 dorsal ridge acute ; mucro subposterior, little elevated. Reddish- 

 olive, maculated with darker and paler. Valves nearly rectangular, 



