THE AUSTEALIAN LAND SHELL, THEESITES BIPAR- 

 TITA, AND ITS ALLIES 



By William B. Marshall 



Assistant Curator, Division of Mollusks, United States National Museum 



Recently Mr. C. Walton of Peterhead, Port Adelaide, South Aus- 

 tralia, presented the United States National Museum with a number 

 of land shells of northeastern Australia and islands in Torres Strait. 

 All of the specimens received belong in the group Thersites {Hadra) 

 hipartita Ferussac. They present a great variation in size and form^ 

 and the color varies from bipartite (whitish spire, chocolate base) to 

 specimens which are entirely pale straw color, and to others which 

 are entirely dark chestnut, and to others which are chestnut 

 above, darker, sometimes nearly black below. Most of them have 

 a white or pale spiral band at or near the periphery, and a dark 

 band just below the suture. When the mass of material now 

 in the Museum collection is arranged in geographic sequence, many 

 characteristics which hitherto have escaped attention become evident, 

 and show plainly that specialization has taken place along certain 

 definite lines, and requires the recognition of additional species and 

 subspecies to properly understand the problem presented. Pilsbry in 

 his first study of Thersites 'bipa/rtita ^ placed it in the genus Ga/maena^ 

 subgenus Eadra^ section Hadra s. s., and gave^ the following note : 



The main feature distinguishing Hadra from Chloritis is that the apex in the 

 former is neither concave, notably flattened, nor sculptured. This group seems 

 more justly regarded as a subgenus of Chloritis than as a separate genus. 

 Hedley suggests to me that the microscopic sculpturing of Hadra is a reminis- 

 cence of the hair granules of Chloritis. 



Later in his analysis of the Mparfita group ^ he places it in the 

 genus Thersites, subgenus Thersites, section Hadra and uses the fol- 

 lowing names : 



Hpartita Femssac-h semibadia Albers 



form unicolor Cox 



form minor Pilsbry 



var. semicustanea PteiEer-{-fumculata Pfeiffer 

 forsteriana Pfeif£er-\-hetaera Pfeiffer 



form major Dohrn 

 darwini Brazier. 



1 Manual of Conchology, vol. 6, p. 276, 1892. 

 ''Man. Conch., vol. 2, p. 132, 1894. 



No. 271 1.— Proceedings U. S. National Museum, Vol. 72, Art. 15. 



55223—27 ^ 



