280 PLANAXIS. 



This appears to be an undoubted inhabitant of fresh water, and 

 as such is an interesting novelty ; but are not its affinities with 

 Melanopsis rather than with Planaxis ? 



Subgenus QUOYIA, Desh., 1830. 

 P. DECOLLATUS, Quoy. PI. 53, figs. 71, 70. 



Strongly spirally grooved, grooves stronger on the base ; colum- 

 ellar lip excised above; epidermis olivaceous, with, dull chestnut 

 obliquely longitudinal strigations ; apex decollated. 



Length, 28 mill. 



Philippines, Ascension IsL, New Guinea. 



It is Monoptygma melanoides, Lea, and P. Michaui, Crosse and 

 Fischer (fig. 70.) The latter is founded on a younger specimen, in 

 which a chestnut peripheral band appears, and the interior of the 

 outer lip is not ridged ; both these characters merge into the normal 

 type of the species with increasing age. 



Subgenus HOLCOSTOMA, H. & A. Ad., 1853. 

 P. PILIGERUS, Phil. PL 53, figs. 62, 69. 



Smooth, under a bristly epidermis, yellowish brown, with two 

 chestnut bands, outer lip dentate within. Length, 8 mill. 



Mauritius. 



The first figure is from an adult denuded of epidermal hairs, the 

 second represents H. setigerum, A. Ad. (fig. 69), which is said by 

 Mr. E. A. Smith, of the British Museum, to be identical ; if so, it 

 must be a much-magnified figure of a young shell which has not 

 yet acquired the teeth to the outer lip. 



Unfigured Species of Planaxis. 



P. INCISUS and P. T^ENIATUS, Phil. Hab. unknown. 



P. NUCLEOLA, Morch. West Indies. 



P. BUCCINEA, A. Ad. West Indies. 



P. GOULDI, Smith (P. cingulatus, Gld., not Ads.) Japan. 



P. AREOLATUS, Lesson. Tahiti. 



P. HKMiLJEVis, Martens. Socotra. 



P. EBENINUS, Menke. Peru. 



Subfamily LITIOPINTK. 

 Genus LITIOPA, Bang., 1829. 

 L. MELANOSTOMA, Rang. PL 53, figs. 72-75, 78. 



Whorls about 9, slightly convex, towards the apex microscopi- 

 cally longitudinally costulate, other whorls very finely spirally stri- 



