ODOSTOMIA. 171 



C. clathrata: pale reddish, short; ribs rather straight, few 

 cross-bars in the intervals. 

 Y. Odostomia. — The shells of these lively little molluscs 

 are smoother and less turreted than those of the preceding 

 genus ] they have fewer whorls, and a spiral fold on the inner 

 lip. This last character distinguishes them from the shells 

 of Rissoce. The species are — 



0. nitida, 0. unidentaia, 0. Eulimoides, 0. glabrata, 0. pal- 

 lida, 0. ohliqua, 0. Warrenii, 0. Rissoides, 0. inscidptaj 

 0. cylindracea, 0. alba : the shells of these are smooth, 

 and rather oval. 

 0. conoidea, 0. conspicua, 0. acuta, 0. clavulus, 0. plicata, 



0, truncatula: smooth, and more or less conical. 

 0. striolata, 0. dolioliformis : spirally striated. 

 0. inter stincta, 0. spiralis, 0. excavata, 0. decussata: sculp- 

 tured in both directions. 

 Some of the above species in each group are very difficult 

 to distinguish from each other, and some of the latter are 

 not very different from Chemnitzia. The animals resemble 

 the latter genus in all essential particulars; they are all 

 brisk little creatures, not at all shy in captivity, but moving 

 about, showing all their parts freely. They live in rather 

 deep water, and, like the Chemnitzice, begin their shell in a 



