12 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxx. 



.specios agree in one character only, namely, the discoid method of 

 growth. 



Ainplexo'pora discoidea is readily recognized by its discoid habit of 

 growth, absence of mesopores and by rather numerous acanthopores 

 and diaphragms. 



Occurrence. — A characteristic fossil of the Fairmount member of 

 the Covington group at Cincinnati, Ohio, and vicinity. 



AMPLEXOPORA FILIOSA (D'Orbigny). 



Plate III, figs. l-M. 



Monliculiporti filkuna D'Orbigny, Prodr. de Pal., 1, 1850, p. 25. 



7yepto<r(//)a yi^tosa Ulrich, Geol. Surv. lUinoi.'!, VIII, 1890, p. 45(3, \)\. xxxvr, figs. 



7, 7a. 

 M(mtlculipor<t Ji/idsa James and J.\.ves, Juur. Cincinnati Soc. Nat. Hist., X, 1888, 



p. 162.— J. F. Jame.s, Jour. Cincinnati Soc. Nat. Hist., XV. 1893, p. 158. 

 Aiiip/c.ropora Jiiiosn NicKLEs and Basslek, Bull. U. S. Geol. Hurv., No. 178, 



1900, p. 164. 

 Muiitlculipora .vihcj/lindrlrji. (U. P. James, Ms. ) J. F. James, Jour. Cincinnati iSoc. 



Nat. Hist., XVIII, 1896. p. 128, fig. 18a-c. 



The type lot of James's Motiticullpora KKhcyllndrica consists of two 

 specimens, one of which is an example of Dekayella alrichi and the 

 other — the one from which his illustrations were prepared — pi'oves 

 to be the same as Aniple.wjxn'a Jilloxa (D'Orbigny). Under the cir- 

 cumstances, only the figured specimen should or can be considered as 

 the type of James's species. As this is an unquestionable example of 

 A.Jiliosa, a species described long before by D'Orbigny and well 

 known to Cincmnati collectors, James's J/, siihcyllndrlca naturally 

 falls into synonymy v^x^'ix A. jiliom. The untigured specimen resem- 

 bles the figurcMl type only in that it is a thick subcylindrical stem. In 

 all other respects it differs decidedly and shows the characters of 

 Dekayella idrichl. (Plate II, figs. 3, 4.) The figured specimen differs 

 from the ordinary masses of Aiiiplexopora jillosa merely in this, that 

 in growing over and completely covering an OrtJioccras it tinally 

 assumed a subcylindrical shape. This is not an unusual occurrence, 

 though the majority of specimens are irregularly massive or hemi- 

 spheric in shape. J. F. James has illustrated the internal characters 

 of the specimen regarded as the type of his species, but thin .sections 

 of the same prepared by the writer show thnt his figures are not only 

 misleading but also incorrect. On Plate III of this paper the views 

 presented by these thin sections have been carefully drawn. 



Ariiph',vo)>or(i JiJiom is a characteristic and not luiconnuon fossil 

 ranging from the Fairmount to and through the Corryville members 

 throughout the Ohio Basin, and may readily be recognized by its mas- 

 sive zoaria, monticulated surface, thin-walled polygonal zo<ecia and 

 absence of mesopor(\s. The size of th(> zoarium in spiM-imens seen by 

 the w liter lias varied from lumps less than 2.5 mm. in diameter to 



