boettgkr: on sulcobasis coxcisa. 187 



New Guinea, is based on an error, and cnmingi is confined to the 

 Am Islands. As shown above under S. coficisa riihra (Alb.) the 

 misunderstanding of cnmingi from the xiru Islands was caused by 

 Albers, who quoted his rubra from an erroneous locality, i.e. the 

 Aru Islands. Misled by this statement, Wallace (1865), followed by 

 subsequent authors, treated the sliells which really came from the 

 Aru Islands as belonging to rubra, but these two forms, rubra and 

 mmivgi, are the very extremes of the group of Sulcobasis concisa 

 (Per.), as a glance at my figures clearly shows. I have before me three 

 specimens of cumingi. The first is one of Gude's cotypes, mentioned 

 above (pi. v, figs. 7-9). The second is in Paetel's collection, 

 belonging to the Berlin ^Tuseiim, and was very kindly sent me by 

 Professor Dr. J. Thiele. It is represented on my pi. v, figs. 10-12, 

 The other specimen was collected by Wallace and handed over by 

 him to H. Dohrn, whose collection now belongs to the Stettin 

 Museum ; Stadtrat Hahne of Stettin kindly gave me an opportunity 

 of studying it. In 1879 Dohrn figured tliis specimen as rubra, and 

 in 1890 Pilsbry copied this figure under the same name. 



8. concisa cumingi (Gude) thus occurs on the Aru Islands, from 

 where certain specimens collected by W^allace are at hand. No 

 certain locality in New Guinea for this sub-species has come to our 

 knowledge, but, if Cuming's statement be correct, we may certainly 

 suppose that it lives in the part of New Guinea opposite to the 

 Aru Islands. 



Summary. 



My investigations show that Sulcobasis concisa (Fer), with its sub- 

 species, is distributed over a bow formed by the Aru Islands, the 

 north-western peninsula of New Guinea, Waigiou, Mysol, the 

 Halmahira group of the Moluccas, and the northern part of Celebes. 

 On the other hand, the species does not occur on another bow, 

 the components of which are often situated very close to that of the 

 bow mentioned above. This second bow, on which our species is 

 wanting, is formed by the Tenimber Islands, the Key Islands, the 

 Amboina group of the Moluccas, and Burn. On the first bow 

 the sub-species of Sulcobasis concisa (Per.) are distributed as follows : 

 S. concisa cumingi inhabits tlie Aru Islands and possibly New Guinea 

 (probably in the nortli-western district northward of the Aru Islands). 

 S. concisa concisa (Per.) is found in the island of Waigiou, in the 

 little island of Bawak, and probably also in the neighbouring little 

 islands. It is also possible that its distribution extends to the 

 neighbouring coast of New Guinea. S. concisa rubra (Alb.) occurs on 

 the bow westward from the island of Mysol ; it lives on Mysol, 

 on the Halmahira group of the Moluccas, and in the north of Celebes. 

 A gradual flattening of the shell may be observed in specimens found 

 on the bow from the Aru Islands to the west. S. concisa cumingi 

 exhibits the highest, S. concisa rx(hra the lowest spire. The 

 other sub-species graduate very conveniently between these two 

 extremes. 



