April, 1920] Marl Deposits in Ohio 181 



and keeled at the periphery; evidently they had been 

 injured, and then formed a premature aperture, of almost 

 normal configuration. All are remarkably alike, and 

 resembling ovata more than morsei, but a careful exam- 

 ination reveals their nature. 



This, the largest of the vertigos, has a rather restricted 

 area of distribution, recent, so far as known: Michigan, 

 northwestern Ohio (Castalia), and northeastern Indiana. 

 It should be looked for also in marls of other states. 



Vertigo elatior Sterki, common; some specimens are rather 

 small, short, but still different from ventricosa Morse, at 

 the basal part, and with the palatal callus and plicae 

 stronger. It is widely distributed as recent, and found also 

 e. g., in loess of southern Indiana, collected by Mr. A. A. 

 Hinkley. 



Vertigo tridentata Wolf, one shell, like the originals from Illinois. 



Vertigo milium Gould, a few, of different shapes: some rather 

 ventricose, others narrowly cylindrical. 



Succinea ovalis Say, frequent, with a short spire, form totteniana 

 or near. 



Succinea retusa Lea, frequent, small and mostly young; differ- 

 ent forms; a few with the whorls rather ventricose, the 

 majority narrow with the whorls flattened; the latter 

 appear to be of the form decampi Gould (Dr. Walker). 



Succinea avara Say, rather scarce; near the common, or typical 

 form with the whorls well rounded; not chalky but like 

 fresh, a few reddish, the others pale corneous. 



Succinea avara? peculiar form, possibly distinct; larger, 

 8-10 mm. long, with 4-4^^ rather fiat whorls; the spire is 

 long and very slender. All of these are chalky, as are also 

 L. ovalis and retusa. 



Carychium exiguum Say, abundant, variable as to size and 

 shape; generally somewhat small, 1.5-1.9 mm. long; some 

 are ventricose with the penultimate and middle whorls 

 large, others narrowly cylindrical or turriculate, resembling 

 exile. 



Carychium exile Lea, rather scarce; some appear not to be 

 characteristic and are doubtful; their rib-like striae are 

 slight and irregular. 



