FLAMMULINA. 11 



Flammulinas. In no case does the ectocone unite with and ascend the 

 mesocone on the marginals as is the case in all genera of Zonitidce 

 which retain ectocoues upon the marginal teeth. 



Distribution, New Zealand, New Caledonia, Lord Howe Island? 

 Australia and Tasmania. 



A group of rather small shells differing from Zonitidce in the forms 

 of the marginal teeth of the radula and the plaited jaw, and from 

 Endodonta and its subdivisions in the possession of a well developed 

 caudal mucous gland. The numerous species have been distributed 

 into many groups which are considered genera by some authors, but 

 which intergrade so closely in all essential characters that I am com- 

 pelled to class them as -sections or at most subgenera. Their differ- 

 ential characters seem no more generic than those distinguishing 

 Tachea, Macularia and Pomatia among European Helices, or Meso- 

 don, Triodopsis and titenotrema among American. Genera should, 

 it is believed, be founded upon really tangible structural differences, 

 either in shell, animal or both ; and such differences these groups do 

 not seem to possess. They are however of value as subgeneric divis- 

 ions. The investigation of the genitalia may lead to more satisfactory 

 results, but I expect to find but little differentiation within the 

 genus. 



Our knowledge of these forms and their anatomy is mainly due to 

 Professor F. W. HUTTON and Mr. H. SUTER, who have investigated 

 the dentition of a majority of the New Zealand species. See Hutton, 

 in Trans. N. Z. Inst. xiv, xv, and xvi, and Suter, in Tr. N. Z. Inst. 

 xxiii and xxiv. Messrs Hedley and Suter have revised the nomen- 

 clature in Proc. Linn. Soc. N. S. Wales (2) vii. 



The characteristics of Flammnlina may warrant the surmise that 



they have been modified to occupy in New Zealand the place filled in 



the economy of nature by Zonitidcc in other regions. If this be true, 



the anomalous dentition of Phacussa must be regarded as a recent 



"adaptive modification. 



For the generic title of this group the writer, in 1892, selected 

 Button's name GERONTIA, this being the oldest designation pro- 

 posed for species then known to him to belong to the genus. There are, 

 however, three prior names, Flammulina Martens, which being the 

 earliest is now adopted, and Monomphalus and Rhytidopsi* of Ancey, 

 which are also believed to apply to members of tins genus. The 

 presence of a caudal mucous-secreting gland, however, has not been 

 ascertained in the species of these New Caledonian groups, so that 

 their relationship to Fltnnmnliim- is uncertain. 



