60 PALJEOSTOLOGY OF NEW YORK. 



EUOHPEALUS (PlIANEROTINUS) LAXUS. 



l'l.ATK XVI, KI«S. 8, », 16-18. 



Euoinphalux laxus, Hall. Descriptions of New BpedM of Fossils, etc., p. M. 1861. 



Fifteenth Hep. N. Y. State Cab. Nat. Hist., p. 54, \<\. 8, tg. 2. 1862. 

 (Ecculiomphalwt) laxus, Hall. Illustrations of Devonian Fossils: Gasteropoda, pi. 16. 1876. 

 EcculhnHphalits comes. Hall. Illustrations of Devonian Fossils : Gasteroiioda, pi. 16. 1876. 

 Compare J'hamrutinus paradoxus, Wiscubll. Proc. Acad. Nat. Sci. Phila., p. 21. 1863. 



Shell discoid ; lower side broadly umbilicate. Volutions about four, nearly in 

 the same plane, the inner ones rising moderately above the plane of the 

 outer one, disjoined throughout their entire extent, very gradually and 

 regularly expanding from the apex; section circular. Aperture (so far 

 as known) subcircular, scarcely expanded. 



Surface marked by crowded concentric striae, which are sometimes regular and 

 equal, and on some parts of the shell more closely arranged, and all 

 directed a little forward, from the inner side of the volution. 



The greatest diameter of the largest specimen seen, is one inch and five- 

 eighths ; the prevailing forms have a diameter of about one inch, while many 

 are of smaller size. 



This species differs from any other in this series of strata, except the fol- 

 lowing one, in the distinct separation of the volutions throughout their entire 

 extent. The impressions in stone are strongly marked by the transverse stria?, 

 which are often crowded in fascicles, and the casts preserve fainter impressions 

 of the same markings. 



Recent examinations of the specimens illustrated (ut. cit.) as Ecculiomphalus 

 comes have satisfied me that they are imperfect conditions of E. laxus, having all 

 the external characters of that species except the inner volutions, which have 

 been decollated or removed during the maceration of the shells. I therefore 

 propose to unite these two imperfect forms, figs. 8 and 9, with the typical 

 forms of the species, figs. 17 and 18. 



The Phanerotinus paradoxus (plate 16, fig. 16), described by Prof. WmCHBLL, 

 from the Burlington sandstone of Iowa, is an extremely similar form with 

 E. laxus. The perceptible difference, on comparing casts of that species, is a 



