GUPPY : MOLLUSCA OF TRINIDAD. 229 



55. Helicina ignicoma Guppy. 

 Crosse, I.e., p. 59, No. 58. 



An orbiculate-conoidal radiately sinuate-costelbte reddish 

 or yellowish shell. Height 3 mill., diameter 4|- mill. It 

 belongs to the section typified by H. pHcahda Pfeiff. and H. 

 rugosa Pf. 



56. Cyclas incurva Guppy. 



SphcEiiuni incurvum Maze, ' Journ. de Conch.,' 1874, p. 173. 

 Pisidium inairimm. Crosse, 'Journ. de Conch.,' 1890, p. 61, 



No. 63. 



The Martinique examples sent me by H. Maze are un- 

 distinguishable from ours. 



57. Cyclas punctifera Guppy. 

 'Ann. and Mag. Nat. Hist.,' 3 ser., vol. xix., p. 160 (fig.). 

 Pisidium ptoidifenim Crosse, 'Journ. de Conch.,' 1890, p. 60, 



No. 62. 



The Pisidium simile of Prime (Guadelupe) appears to me 

 identical. 



The questions as to whether these shells should be called 

 Pisidium or Cyclas resolves itself into the question of how far 

 generic names are to go. I readily admit the subdivision of 

 genera to any reasonable extent, but the names given to the 

 subdivisions should not be accorded generic rank. This is a 

 test case, because Pisidium may be admitted to have a greater 

 claim to be recognised as a substantive division than many 

 others that are frequently used as generic appellations. The 

 question between the use of the names Cyclas and Sphceiiu7n 

 is of another kind altogether. 



58. Anodon leotaudi Guppy. 



Crosse, I.e., p. 61, No. 64. 



I have been at a loss as to what should be considered the 

 nearest relation of our Anodon. I am inclined to think it is 

 A. sirionos Orb. (as A. ferrarisii Orb., Voy. Amer. Merid., pi. 



