NEW ZEALAND rOLlTLACOrnORA. 



191 



A specimen from Campbell Island, belonging iindonbtedly to the 

 same species, is of olive-brown colour, the jugum horny-yellow. 

 The anterior valve has Avell-pronounced radiating riblets, the con- 

 centric lines on all the valves are less distinct, and the posterior beak 

 on the central valves is almost obsolete. The ribs on the lateral area 

 of the intermediate valves do not run down to the margin, but are 

 intercepted by a broad, smooth, concentric band, extending along the 

 sides and antei'ior part of the valves. The valves are more depressed, 

 divergence 135°. 



^rvfrn 



10. 



n 



Plaxiphora sithafrata, Pilsbry. 



7. Nat. size, from spirit specimen. 



8-10. Ventral view of anterior, median, and posterior valves. 



11. Portion of dorsal surface of fom-tli valve. 



Hal. — ^[acquarie Island (A. Hamilton) ; Campbell Island. 



The ^rac(|uarie Island specimens are mostly covered by a thick, 

 white coralline growth, the Campbell Island specimen with Polyzoa. 



The specimen from which the figure is di'awn is in the Otago 

 Museum ; the valves are fi'om specimens kindly given to me by Mr. A. 

 Hamilton. 



This may be the Plaxiphora Camplelli, Filhol (Compt. Rend., xci, 

 1880, p. 1095; Pilsbry, Man. Conch., ser. I, vol. xv, p. 107). 



