KEPOKT ON THE POLYPLACOPHOKA. 11 



Valva postica. sub apice concava, postice sinuata. Zona minima, spiculis tenuibus versus 

 marginem munita. Lod. 10 - 0. Lat. 3 - mm. Div. 90°." 



"North Pacific Ocean, in lat. 53° 08' N, Ion. 171° 19' W., at a depth of 1006 fathoms ; 

 black sand and shells. Brought up in the sounding-cup by Capt. Geo. E. Belknap, 

 U.S.N., on the sounding expedition of U.S.S. 'Tuscarora' in 1874, bottom temperature 

 35° - 5 F. - (Specimens obtained by H.M.S. Challenger in Balfour Bay, Royal Sound, 

 Kerguelen Id., Southern Ocean, in 20-60 fins., for examination of which I am indebted 

 to the courtesy of Rev. R. J. Boog Watson, are apparently identical with Captain Belknap's 

 species.)" Loc. cit., p. 317. 



I have quoted the last paragraph in full, as Dall refers to some Challenger specimens. 

 I received only one minute specimen from Kerguelen Island, which will be found to differ 

 considerably from Leptocldton belhiapi. It is most probable that Dall refers to the two 

 specimens from off the Philippine Islands which I have identified as Leptochiton belknapi. 



Locality.— Station 205. November 13, 1874. Lat. 16° 42' N, long. 119° 22' E. Off 

 Cape Bolinas, Luzon, Philippine Islands. 1050 fathoms. Blue mud. Bottom tempera- 

 ture 37°. 



Shell. — Brittle, closely covered with large round smooth tubercles. The sides meet at 

 an angle of about 110°. Sutural laminse small. 



Anterior valve. — With a few irregular lines of growth, thickly covered with irregularly 

 disposed tubercles. 



Intermediate valves. — Central areas : with a shallow depression on each side of the 

 median ridge, which gives the latter a pinched appearance; this depression is most 

 apparent at the hinder border of each valve. The tubercles have a general arrangement 

 in oblique lines radiating forwards from the keel, and at the same time in lines concentric 

 to the umbo, but these two series of lines are not always regular, and the tubercles often 

 appear to be irregularly disposed. A series of short concentric rows usually demarcate 

 the anterior border of the lateral areas. Lateral areas : scarcely apparent ; a groove indi- 

 cating a line of growth occurs at a short distance from the girdle ; tubercles irregularly 

 disposed, with a tendency, however, to concentric lines. 



Posterior valve. — With a small subcentral umbo, behind which is a slight depression. 

 Anterior area: the lateral longitudinal depression causes the jugum to be slightly 

 prominent, and thus gives the anterior area a somewhat trilobed appearance ; the tubercles 

 radiate from the rounded keel. Posterior area: with concentric lines of growth and 

 closely set tubercles. 



Girdle. — Narrow, thickly covered with delicate small oval scales : longer, narrower, 

 and more pointed scales occur along the border, and in the angles between the valves. 



Colour. — Greyish white. 



Size. — Length about 12 mm. ; breadth, 5 mm. ; height about 2*5 mm. 



Gills. — Forming a short posterior row, six or seven in number. 



