172 



Remarks : — M. smithi is closely allied to M. cylmdrica Smith ^), but is distinguished by 

 the shell being smaller, less inequilateral, not so tumid, and the outline more regular. The 

 sculpture of the two species is also différent. 



2. Montaatta pelseneeri sp. nov. (Plate V; fig. 28). 



191 1. Montacudde} St. 50, Pelseneer, "Siboga" Lamellibranches (Anat.), p. 47. 



I associate this interesting species, which is represented by a complète right and a broken 

 left valve, with the name of Dr. P. Pelseneer of Brussels. 



M. pelseneeri is closely allied to M. vennsta Lynge ") but the shell is much thicker, 

 coarser, and is somewhat compressed behind the middle. The ventral margin is more arcuate 

 and the shell is more acuminate anteriorly. The sculpture also is more pronounced ; it consists 

 of somewhat irregular, concentric striae, which are just visible to the naked eye. 



Measurements of the Holotype : — Length 5.2 mm., height 3.5 mm., diameter of right 

 valve 1.4 mm. 



Habitat : — The unique Holotype was dredged in the Bay of Badjo, west coast of 

 Flores (St. 50). 



3. Montacuta [My sella) paula (A. Adams). 



1856. Pythina paitla and P. peailiaris Adams, A., Proc. Zool. Soc. London, p. 47. 



1857. Pytliina paula Adams, H. & A., Gen. Rec. Moll., II, p. 476. 



1885. Montacuta paula Smith, "Challenger" Lamellibranchia, p. 203, pi. XII, figs. l, \b. 



l8go. Pythina pailla and P. peculiaris Paetel, Cat. Conch. Samm., III, p. 132. 



1891. Pythina paula and P. peculiaris Smith, Ann. Mag. Nat. Hist., (6) VIII, p. 230, pi. XII, 



figs. I, \a, b. 

 1902. Pythina paula Shopland, Proc. Malacol. Soc. London, V, p. 178. 

 1906. Pythina paula var. peculiaria Melvill & Standen, Proc. Zool. Soc. London, p. 816. 

 1909. Alontacuta [Tellimyà) paula Lynge, D. Kgl. Dansk. Vidensk. Selsk. Skr. Nat.-Math., 



(7) V, p. 182. 

 1911. Montacuta [Tellimyà) paula Pelseneer, "Siboga" Lamellibranches (Anat.), p. 45, pi. XVI, 



fig. 6. 



A single broken left valve from Macassar (St. 71) is undoubtedly a young shell of 

 Montaatta [Mysella) paula. I hâve examined the types of M. paula and M. peculiaris in the 

 British Muséum, London, and agrée with Smitpi that the latter species is based on only an 

 "unusually distorted" shell of the former. 



Distribution : — M. (M.) paula has been recorded from Aden, Ceylon, Gulf of Siam, 

 south of New Guinea and Torres Straits. 



4. Montacuta [Mysclla) sibogai sp. nov. (Plate V, figs. 29, 30). 



M. {J\d i) sibogai closely resembles M. {Ti) ar ouata (A. Adams)*), but is easily distinguished 

 by its shell being more triangular, comparatively deeper than long, anterior and posterior 

 sides more sloping, ventral margin more arcuate, and the regular concentric sculpture more 

 strongly developed. 



I Smith, E. A. — • "Challenger" Lamellibranchia, p. 206, pi. XII, figs. 4, 4^,1'' (1885). 



2) Lynge, H. — D. Kgl. Dansk. Vidensk. Selsk. Skr. Nat. Math. (7) V, p. 181, pi. III, figs. 28, 29 (1911). 



3) Adams, A. — Proc. Zool. Soc. London, p. 47 (1856). I figure a shell of this species (Plate V, figs. 31, 32), magnified three times. 



