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Subgenus Pteromeris Gonrad. 

 Y-^V.-^RldAEDlA (PT. .- -13) AOAZ^IS Dall. 



Ymc-ricarclia ( Ptr-romeris } a carls Dall, 190r'', ^rans. ' — ■.ler ?vee 

 Inst. Soi., Philadelphia, vol. ?, pt. G, p. 14:^4, pi. 

 - ^6, ■--. 4. 



Desc^ription .- "Shell : , plump, inequilateral, the full 



"out rather low beaks situated near the posterior third; anterior 

 end lonp-er, ohliquely produeecl, roujade'", posterior dorsal border 

 descending' iiaiieh more steeply, subangular at the lower posterior 

 termination; sculpture of about eighteen broad, flattene'l r^/lial 

 ribs sei.iarated by narrow sulci and arossei by small, arctrnte, rais- 

 ed threads, eonves' dorsal ly, the ends of these threads ■■-'ro.-ecti- • 

 sometimes gives a punctate eff e :• ' ' " '"' -i; there is a small, 



narroY/ luuule and escutcheon anparently quite smooth; hinge normal, 

 the lateral distinct; the inner margins sharply orenvl^fe , the 

 ligament and resilium v/holly external. Length 2.5, f-^-^-i-ght 2.5, 

 diameter 2.0 mm." 



"This little shell is '-p rdly 3 tyriic -9I ?t'-rom.pris, bi:it is 

 poesesse -; of all the essential characters and nv ' regarde'"; a.s 

 the precursor of the group. L^he posterior bea)rs are very oharac- 

 t^rip.tic ■PpntT-'^s as v/ell as the -^ist^-ict latpmlF;-. ^t is the 

 earliest knovm ancl smallest of the species." l-Jall, l^C"^), 



