644 bartsch: classification of helicinidae 



which helped materially in the fixing of the majority of the old 

 names. 



The members of the family Helicinidae found in the Philippine 

 Islands belong to the subfamily Helicininae, which in turn 

 breaks up into five genera; namely, Ceratopoma, Pleuropoma, 

 Sulfurina, Geophorus, and Kosmetopoma. 



All of these genera are based upon opercular characters which 

 appear wonderfully constant. ' 



Of these genera, Ceratopoma Mollendorff has the least special- 

 ized operculum, for here we find a simple thin transparent 

 homy shield without calcareous deposit. The type of this 

 genus is Helicina caroli Kobelt. 



In Pleuropoma Mollendorff the operculum is still simple, i.e., 

 a horny shield, but there is in addition a slight deposition of cal- 

 careous material. A flexuose ridge extends close to the margin 

 in a sigmoid curve from the columellar border along the parietal 

 edge. This gives the edge of this portion and in some species 

 the entire operculum the appearance of being double. The type 

 of this genus is Helicina dichroa Mollendorff. 



In Sulfurina Mollendorff we find the operculum similar to 

 that of Pleuropoma but the calcification is stronger and the 

 flexuose line is replaced by a strong raised keel which is usually a 

 httle farther removed from the edge. The type of this genus is 

 Helicina citrina Sowerby. 



In typical Geophorus the operculum is much thickened by cal- 

 careous deposits. The columellar border bears a deep groove, 

 giving this portion the appearance of being double. 



This groove frequently extends for a considerable distance 

 along the two long sides. The outer portion at the columellar 

 border is frequently a little shorter than the inner, and at times 

 considerably thickened, particularly at the posterior columellar 

 angle, where even a knob develops in some forms. The above 

 characters apply to Geophorus in the restricted sense as typified 

 by Helicina agglutinans Sowerby, the genotype. There are, how- 

 ever, two modifications of this form of operculum, one in which the 

 columellar border is thickened into a strong knob at the parietal 

 edge on the outside, which is hmited anteriorly by a slit or deeply 



