Oliver. — Mollusca of the Kermadec Islands. 547 



Habitat. — Abundant living on rocks near low-water mark, Sunday 

 Island. The shells almost always covered with crustaceous algae, and 

 sometimes found attached to shells of Scutellastra kermadecensis. In its 

 depressed form it resembles a number of marine molluscs inhabiting the 

 lowest portion of the littoral belt. 



Siphonaria macauleyensis n. sp. Figs. 42 and 42a. 



Description of Type Specimen. — Shell irregularly ovate, high, conical, 

 height 0-48 of length. Anterior slope long, arched ; posterior slope steep, 

 nearly straight. Apex nearly two-thirds the length of the shell from the 

 anterior end, and to the left of the central line, directed backwards. Margin 

 fairly regularly crenulated. Siphonal groove scarcely projecting. Sculp- 

 ture : About 45 close nearly regular radiating ribs, two on the siphonal 

 groove and a few others here and there on the posterior half larger than 

 the others. All crossed by concentric growth-lines. Colour : Above grey, 

 the ribs nearly white. Interior whitish in the centre, muscle-impression 

 brown, followed by a whitish band and a dark-brown margin crossed by 

 white bands opposite the ribs. 



Length, 19'6mm. Breadth, 146 mm. Height, 9'5 mm. 



Variations from Type. — There is a good amount of variation in the shape 

 of the shell, prominence of the ribs, and especially of the siphonal groove, 

 which sometimes projects a considerable distance. When this is the case 

 with depressed forms they come very close to the subspecies perplexa. 

 The depth of colour inside varies, some examples having the central portion 

 all brown. The following measurements show variations in the shells : 

 (a.) Length, 19-5 mm. ; breadth, 16-2 mm. ; height, 10 mm. ; ratio height 

 to length (L.=100), 0-51. (b.) Length, 19-3 mm. ; breadth (behind siphonal 

 groove), 15*5 mm. ; height, 6-2 mm. ; ratio height to length, 0*32. 



A few specimens which I collected on French Rock apparently belong 

 to this species. They are larger than those from Macauley Island, and all 

 have the upper surface either corroded or covered by coralline algae, so 

 that the sculpture is obscured. The general shape and the colour of the 

 interior, however, agrees with Macauley Island specimens. Length, 23 mm. ; 

 breadth, 18-5 mm. ; height, 8*3 mm. 



S. macauleyensis comes very close to S. exulorum from Norfolk Island, 

 differing principally in the more irregular shape and ribbing, and in the 

 more posterior position of the apex. S. zealandica is also allied, but easily 

 distinguishable from the above two. 



Habitat. — Living on rocks between tide-marks, Macauley Island (type 

 locality) and French Rock ; common. A few specimens were also obtained 

 on Sunday Island. 



Subsp. perplexa n. subsp. Figs. 43 and 43a. 



Recorded, Iredale, Pro. Mai. Soc, ix, 71, 1910 (S. atra). 



Description of Type Specimen. — Shell depressed, height 0-29 of length, 

 ovate, left side slightly rounded in the centre, sloping sharply away at 

 either end, right side semicircular. Apex subcentral. Slopes slightly 

 arched. Margin irregularly crenulated. Siphonal groove high, angular, 

 and projecting for a distance equal to one-third of that between margin 

 and apex. Sculpture : Irregularly spaced straight or wavy radiating ribs, 

 about 20 principal ones, including 2 on the siphonal groove. They are of 

 various sizes, those on the left side and alternate ones on the posterior half 



18* 



