22 AMPHINEURA. [Polyplacophora. 



broader at the sides, leathery, tan colour, dark brown or black when 

 dry, with sutural pores with long corneous bristles, 2 to 6 in a tuft, 

 and a second row of alternating tufts and bristles along the margin ; 

 in front of the end valves 6, rarely 5, smaller pores. Colour reddish- 

 olive, maculated with darker and paler ; or reddish-brown, the jugum 

 dirty-pink or with a wedge-shaped white stripe with a brown one in 

 the centre. Interior white tinged with blue, or distinctly blue ; 

 anterior valve with 8 irregularly placed slits ; teeth sharp, striated 

 on the outside ; intermediate valves with 1 slit on each side, the 

 posterior tooth broad ; posterior valve with a rounded elevated in- 

 sertion plate and a narrow sinus in the middle behind. Sinus narrow, 

 short ; sutural laminae continuous over the anterior false apex. 



Length, 60mm.; breadth, 40mm.: divergence, 110. Length, 

 75 mm. ; breadth, 45 mm. : divergence, 125 (subatrata). 



Type in the British Museum (Cuming collection, No. 2). 



Hal. Auckland Islands, Campbell Island (Captain Bollons) ; Mac- 

 quarie Island (A. Hamilton). 



Remarks. The species was described in MS. by Carpenter, and pub- 

 lished by Pilsbry, who considered it to be a synonym of P. biramosa. 

 In 1897 I published a note (P. Mai. S., ii, 188) saying that I could not 

 share Pilsbry's opinion, and that P. superba was much nearer P. sub- 

 atrata. When describing the latter species I had only dry, badly pre- 

 served specimens from Macquarie Island and one spirit specimen from 

 Campbell Island at my disposal, and in all these the valves are much nar- 

 rower than in the type. Captain Bollons has of late most kindly brought 

 well-preserved specimens from Campbell and Auckland Islands, and 

 the study of this material has convinced me that P. subatrata cannot 

 be considered a distinct species not even a valid subspecies. The shape 

 of the intermediate valves is subject to great variability, from very 

 narrow and high to very wide and low, but all intermediate grades 

 occur, and I found it perfectly useless and next to impossible to separate 

 the two forms. The proportion of the longitudinal to the transverse 

 width of the valves I found to vary from 1:2 to 1:3. 



This species may be P. CampbeUi, Filhol (Compt. Rend., xci, 1880, 

 1095), which, however, is quite insufficiently described, and has never 

 been figured. 



The specimens from Macquarie Island have the valves thickly 

 covered by Nulliporites, those from Campbell Island by Polyzoa. 



Sect. 2. GUILDINGIA, Pilsbry. 



Gmldingia, Pilsbry, Man. Conch. (I), xiv. 1893, 312, 329; and Dall, U.S. 

 Nat. Mus., 1881, 284. 288. Type : G. obtecta, Pilsbry. 



Shell and girdle like Plaxiphora, except that the valves are partly 

 immersed by the encroachment of the girdle. 



