40 THE VOYAGE OF H.M.S. CHALLENGEE. 



Waldheimia, King. 



Waldheimia kerguelenensis, n. sp. (PI. III. figs. 1-9). 



Terebi-atula glolosa, Sow. (not of Lamarck), Thesaurus Conchylionun, PL Ixxi. figs. 99-101, 1846. 



Shell ovate, ventricose, longer than wide, yellowish-white, smooth. Dorsal valve 

 most convex near the umbo ; a broad slight mesial depression or sinus commencing about 

 the middle of the valve, extends to the front, more or less distinctly margined on either 

 side by a faint raised line or ridge ; front line slightly depressed and nearly straight. 

 Ventral valve rather more convex than the opposite one, and more or less distinctly or 

 prominently keeled by the presence of a wide convex but slightly raised fold which 

 corresponds with the depression in the dorsal valve. Beak moderately produced and 

 incurved, truncated by a small circular foramen margined laterally by two small disunited 

 deltidial plates. The cardinal process is prominent, and formed of three distinct parts. 

 In the interior of the dorsal valve, and under the incurved extremity of the unibone, hinge- 

 plates wide, septum very short and massive, triangular, wide posteriorly, tapering to a point 

 anteriorly. A pair of muscular impressions, left by the adductor muscles, are present on 

 either side of the sejDtum, at the bottom of the valve. Loop delicate, elongated and reflected. 

 Shell perforated by numerous minute canals. Length 44, width 34, depth 29 mm. 



Habitat. — Waldheimia kerguelenensis was dredged alive by the Challenger Expedition 

 at the following localities : — 



Off Marion Island, west of Kerguelen Island (PI. III. figs. 3-9). 



On the 26th December 1873, at a depth of 100 fathoms, two specimens of Platydia 

 anomioides were attached to examples of the species under description. 



At Station 149, Balfour Bay, near Kerguelen Islands, lat. 49° 16' S., long. 70° 12' E., 

 on 19th January 1874, in 20 to 60 fathoms. Also at Station 150, south of Kerguelen 

 Island (PI. III. figs. 1, 2), February 2, 1874, lat. 50° 4' S., long. 71° 22' E., at a depth of 

 150 fathoms. Bottom temperature, 1°'8 C. Eock. Three examples of Rhynchonella 

 nigricans, var. pixydata, were obtained with it. Waldheimia kerguelenensis was abundant 

 at both localities, but the largest examples were dredged at Station 150. 



Observations. — I have examined several specimens of this species, dredged alive by 

 the Challenger Expedition. It varies in dimensions from 2 to 44 mm. Some examples 

 were nearly circular, and as broad as long, but the majority were of an elongated oval 

 shape, becoming ventricose with age. When the peduncle by which the shell adhered 

 to foreign bodies was sufficiently long, and did not interfere with its limited movements, 

 the beak was much incurved, and the foramen small (PI. III. fig. 1) ; but as in most cases 

 the peduncle was exceedingly short, and came into contact with the hard bodies to which 

 the shell was moored, causing the beak at that part to be worn away, and consequently 

 the enlargement of the foraminal aperture. The animal closely resembles in general 

 character that of Waldheimia fiavescens, so admirably described by Albany Hancock. 



