200 



The "Siboga" Expédition brought up spécimens of this species in deepsea trawls at St. i8 

 (7° 28'. 2 S., I 15° 24'. 6 E., 1018 mètres), St. 45 (7° 24' S., 1 18° 15'. 2 E., 794 mètres), St. 76 (4° 22'.! S., 

 ii8°i6'.9E., 2029 mètres). St. 208 (5° 39' S., i22°i2'E., 1886 mètres) and St. 300 (io°48'. 6 S., 

 i23°23'. I E., 918 mètres). A few young shells from St. 178 (2° 40' S., 128° 37^.5 E., 835 mètres) 

 and St. 211 (5°4o'.7S., I20°45'.5E., 1158 mètres) also appear to belong to this species. 



2. Aéra sibogai sp. nov. (Plate VI, figs. i, 2). 



The following is a description of this new species : — Shell of médium size, thin polished, 

 oblique, elongated ovate; very inequilateral, moderately inflated ; beaks pointed, slightly elevated; 

 lunule elongate, narrowly cordate-, escutcheon narrower, more elongate ; anterior dorsal margin 

 greatly arched ; posterior almost straight; ventral margin slightly arcuate-, anterior end longer, 

 rounded, posterior subtruncate or rounded; cardinal teeth two in each valve, the anterior in 

 right valve much longer than posterior and more oblique; internai ligamental pit long and narrow, 

 almost in line with posterior slope; sculpture consisting of very fine, microscopic concentric striae. 

 Shell of a whitish colour. 



Measurements of Holotype: — Length 13.4 mm., height 11.2 mm., diameter 5.3 mm. 



Habitat: — The Holotype and a few odd valves were brought up in a deep-sea trawl 

 at St. 45 (7° 24' S., 118° 15'. 2 E., 794 metre.s). Other spécimens of the species were obtained at 

 St. 52 (9° 3'. 4 S., 1 19° 56^.7 E., 959 mètres), and at St. 300 (10° 48'. 6 S., i 23° 23'. i E., 918 mètres). 



3. Abra inanis sp. nov. (Plate IX, figs. 13, 14). 



The following is a description of this new species: — Shell of small size, thin, transluscent, 

 polished, trigonal-ovate, inequilateral, moderately inflated; beaks pointed, hardly elevated; lunule 

 very narrow, elongate ; escutcheon more concave, elongated ; bounded by a distinct ridge running 

 almost to posterio-ventral margin of shell ; both anterior and posterior dorsal margins greatly 

 arched; ventral margin very arcuate; anterior end broadly rounded, posterior subacuminate ; 

 cardinal teeth two in each valve, subequal; internai ligamental pit long and narrow, almost 

 parallel to posterior margin of shell; sculpture consisting of low but distinct concentric striae, 

 better developed near the ventral margin. Shell of a whitish colour. 



Measurements of right valve: — Length 20 mm., height 9 mm., diameter 2.4 mm. 



Habitat: ■ — Two odd valves, a right and a left one, were dredged at St. 159 (o°59'.i S., 

 i29°48'.8E., 411 metre.s). , 



Remarks: — A. inanis resembles A. cistîila (Melvill) ^) from the Persian Gulf, but the 

 shell of the "Siboga" species is more trigonal, more inflated, while there is no ridge on the 

 posterior slope in A. cishUa. 



4. Abra weberi sp. nov. (Plate IX, figs. 15, 16). 



This new species is closely allied to A. maxinia (Sowerby) and A. convexior Smith "), 

 but is distinguished from either by its shell being not so elongate, comparatively much higher, 



1) Mei.vill, J. C. — in Melvill, J. C. & Standen, R, Proc. Zool. S.)c. London, p. 825, pi. LVI, fig. 6 (1907). 



2) Smith, E. A. — Ann. Mag. Nat. Hisl., (6) XVI, p. 10, pi. II, figs. 4, 4a (1895). 



