28 HELIX. 



Subsection PLANOGYRA, Morse, 1864. 

 H. ASTERISCUS, Morse. PI. 4, fig. 52. 



Orbicular, somewhat depressed, brownish; whorls 4, well- 

 rounded, crossed by 25-30 thin, transparent, prominent, reclined 

 ribs, the interstices lightly striate, spire not elevated, suture 

 deep ; umbilicus moderate, showing all the whorls. 

 Diam. 1-5 mill. 



State of Maine ; N. of Lnke Superior ; 



Tacoma, Washington Terr. 



Subsection PUNCTUM, Morse, 1864. 

 I. European Species. 



It is very doubtful whether this group should be separated at 

 all from Discus. Certain of the species possess a distinctive 

 character in the jaw, but this organ has not been examined in 

 many of the forms included by Pfeiffer in his undescribed sec- 

 tion Patulastra, which is, at least typically, the equivalent of 

 Punctum. I have retained the species as assigned to the group 

 by Pfeiffer, but many of them are certainly typical Discus, and 

 conchologically there is no gap between the groups. 



IT. MICROPLEUROS, Paget. PI. 6, figs 19-21. 



Minute, openly urnbilicated, somewhat flattened above^ convex 

 below, shining, subpellucid, corneous or amber-colored, costate ; 

 whorls 4, a little convex, with impressed suture, last whorl 

 dilated. Diam. 2 mill. 



Southern France ; Sardinia. 



H. tenuicostata, Shuttleworth, 1848 (= H. Shuttleworthi, Ser- 

 vain), from the last named country, is a synonym. 



H. ELACHIA, Bourguignat. PI. 6, figs. 22-24. 



Very minute, umbilicated, planate above, convex below, pel- 

 lucid, hyaline, light corneous, elegantly costate; whorls 3^-, 

 rapidly increasing, with impressed suture, last whorl slightly 

 descending in front, periphery subangulated, obscurely subcari- 

 nated around the umbilicus. Diam. 1'5 mill. 



Angers, France. 

 H. DEBEATJXIANA, Bourg. PL 6, figs. 31-33. 



Narrowly, deeply umbilicated, subpellucid, a little shining, 

 corneous, with whitish flammules on the earlier whorls, sharply 



