12 THE VOYAGE OF H.M.S. CHALLENGER. 



This species is considerably larger and coarser than the preceding. The tubercles are 

 twice the size, and closer together. The shell is also comparatively sharply keeled, 

 instead of having a gently rounded appearance. 



Leptochiton kerguelensis, n. sp. (PI. I. fig. 3 ; PI. II. figs. 3a-3e). 



Habitat— Station 149c January 19, 1874. Lat. 49° 32' S., long. 70° W. Balfour 

 Bay, Royal Sound, Kerguelen. 60 fathoms. Volcanic mud. Bottom temperature pro- 

 bably 40°. 



Shell. — Minute, smooth, or with scattered minute tubercles; the sides meet at an 

 angle of about 100°; sutural laminae small, triangular. 



Anterior valve. — Small, smooth, with scattered aborted tubercles. 



Intermediate valves. — Central area smooth, with very faint longitudinal striae ; lateral 

 areas scarcely discernible, with faiut radial striae and minute concentric interrupted ridges 

 towards the apex, which pass into inconspicuous small scattered tubercles. 



Posterior valve. — With full rounded umbo, behind which is a shallow depression. 

 Anterior area : similar to the central areas of the intermediate valves. Posterior area : 

 similar to the anterior valve. 



Girdle. — Narrow, with delicate scales. 



Colour. — Uniform whitish. 



Size. — Length, 3 mm. ; breadth, 1-5 mm. 



Gills. — Posterior, eight or nine in number. 



Leptochiton alveolus (M. Sars, MS.) 



Chiton alveolus (M. Sars, MS.), Loven, Ind. Moll. Lit. Scand. Oca, 1846, p. 159. 



Lcpidopleurus alveolus, G. O. Sars, Moll. Eeg. Arct. Norvegise, 1878, p. 110, pL vii. figs. 3a-i, pi. I. 



fig. 7. 

 Leptochiton alveolus, Dall, Proo. U.S. Nat. Mus., 1878, p. 317. 



"Corpus colore nunc pallidiore, albido-cinereo, nunc obscuriore, interdum fere omnino 

 nigro, forma quam solito angustiore, elongato-oblongum, plus duplo longius quam latius, 

 zona perangusta, squamulis inaequalibus, nonnullis spinseformibus. 



"Testa sat convexa, dorso sequaliter arcuato ne vestigium quidem carinas vel arearum 

 lateralium prsebente, valvulis sat elongatis, postica antica majore, semiorbiculari, autice ad 

 lineam rectam truncata, mediis subaequalibus, margine postico recto, antico medio leviter 

 emarginato. Superficies valvularum tuberculis miuutis ovatis regulariter dispositis ubique 

 sculpta. Long. 16 mm." — (G. O. Sars.) 



Habitat. — West coast of Norway, Hardangerfjord, 420 fathoms ; between Lofoten and 

 Bodo, 150 to 300 fathoms (Sars) ; Gulf of St Lawrence, in 220 fathoms, between Cape 

 Rosier and the south-west point of Anticosti Island (Whiteaves) ; St George's Bank, 

 Gulf of Maine, 150 fathoms, U.S. Fish Commission, 1872 (Dall). 



