274 



Gems PLATYOSTOMA. Conrad. 



[Ety. : Platy8,* broad ; stoma, mouth.] 

 (1842 : Joum. Acad. Nat. Sci., Vol. VIII., p. 275.) 



Shell with a short, depressed spire, a large, dilated aper- 

 ture, and with the inner lip lying close against the body- 

 whorl. 



Platyostoma lineata. Conrad. (Fig. 200.) (Pal.N. Y., 

 Vol. V.. Pt. II.. p. 21, PL X.) 



Distinguishing Characters.— -Volutions, four or five; large 

 ventricose body-whorl, which is regularly con vex. and a little 



depressed below the su- 

 ture line; sub-orbicular 

 peristome; thin outer lip, 

 with sharp entire margin ; 

 thickened inner lip. folded 

 and reflexed over the um- 

 bilicus, which in ad nil 



Fig. 200. Platyostoma lineata. 

 views (after Hall). 



Side and top 



s] >< 'cimens is entirely covered ; fine, nearly equidistant, thread- 

 like revolving strire, cancelled by similar concentric striae. 



Found in the lower Moscow shale, at Sections 4 and 5 

 (rare) : in the Encrinal limestone, at Section 5 (common) ; in 

 the Stictopora and Demissa beds, at Section 5 (common, but 

 small); in the lower Trilobite bed, at Section 8 (rare); 

 between the Trilobite and Strophalosia beds, in Avery's 

 Creek ( rather common). 



Platyostoma lineata, var. sinuosa, Hall, has a deep sinus 

 in the peristome, near the umbilicus. 



Found at " Hamburg, on the shore of Lake Erie." ( Hall.) 



Platyostoma lineata, var. emajrginata n. var. (Fig. 

 200A.) (Compare Pal. X. Y., Vol. V., Pt. II.. PI. X.. 



Fig. 



1.) 



Distinguishing Characters. — Spire and volutions similar 

 to /'. lineata; bodv-whorl less ventricose: the last whorl 



*Tln- correel orthography for this name is Flatystoma, but this name was preoccupied 

 for a Bhell by Klein, in 1753 : for an insect by Meigen, in 1808 ; and for a fish by Agassiz, in 

 1829. Paul Fisher, in 18^5, proposed the name Diaphorostoma, in his "'Manuel deUoncuyli- 

 ologie.'' 'I lii- lias been adopted by some authors. 



