Z PEOCEEDINGS OF THE NATIOlSTAIj MUSEUM vol.72 



Dr. James C. Cox ^ treated Thersites hifortita and semicastanea as 

 distinct species, but under the latter he says : 



This species, unquestionably a modified H. bipartita, is so variable that a 

 dozen vpell-marked varieties might easily be selected from among the hundreds 

 of specimens novr before me. I haye taken the preceding description from a 

 Lizard Island specimen. 



He also treats funiculata as a distinct species, but under semi'- 

 castanea he says : " H. funiculata, described elsewhere, I would refer 

 to this head without hesitation. * * *." 



The land shells from the Northeastern coast of Australia and ad- 

 jacent islands, the largest of which heretofore have been called Ther- 

 sites hipartita Ferussac and the smaller ones either positively or 

 doubtfully subspecies of that species, have been analyzed in this 

 paper. It should be remembered that the region includes not only 

 the mainland of northeastern Australia but some of the islands off 

 the east coast of Queensland and the islands of Torres Strait. Tor- 

 res Strait is about 80 miles across and crowded with reefs, shoals, 

 and islands. Isolation and environment undoubtedly have been ef- 

 fective causes producing the characteristics of the various subspecies 

 of moUusks living on these islands. 



Restricting ourselves now to specimens known or believed to come 

 from islands in Torres Strait, we find that so far as known they may 

 be divided into two great groups, one of which is characterized by 

 being large, pale, angular at the periphery and with the spire but 

 little lighter than the base. This group includes two species, both 

 new, described in this paper under the names Thersites waltoni and 

 Thersites dalli. The second group, characterized by being smaller, 

 the spire dark reddish in color, the base much darker, sometimes 

 nearly black, and with the periphery rounded, or at least less angu- 

 lar. This group includes three species, namely: T. setnicastanea 

 Pfeiffer, T. hartschi Marshall, and T. funiculata Pfeiifer. The first 

 two are divided into two or more subspecies. Shells from Lizard 

 Island on the east coast of Queensland resemble these dark shells 

 from the islands in Torres Strait, which, however, are easily dis- 

 tinguishable by their very dark colors and unctuous appearance. 



In the group of Thersites hipartita we now recognize the follow- 

 ing species and subspecies : 



THEESITBS (HADRA) 



Mpartita hipartita Ferussac. 

 hipartita minor Pilsbiy. 

 hipartita unicolor Cox. 

 semicastanea semicastanea Pfeiffer. 

 semicastetwa ahna, new. 

 funiculata PfeifCer. 

 lizardensis lizardensls, new. 



«Moiiogi-aph of Australian Land Shells, p. 56, 1868. 



