34 The Paleontologist. \_yune lo, 



ance is, as if soft mud, forming the strata, had deposited gently around 

 the plants without disturbing their erect position. 



The slab specimens used for- this description vary from ]^ to over ^^ 

 an inch in thickness, surface slightly undulating. On the under side the 

 plants are broken off even with the surface, or leaving small, shallow pits ; 

 on the upper side they are elevated from half a line to over one line. 

 Other markings, on the upper surface, resemble Annelid trails. 



Position and locality : Upper part of the Cincinnati Group, Lower 

 Silurian formation. Dearborn county, Ind. 



GENUS ASTYLGSPGNGIA. Roemer. 

 AsTYLOSPONGiA SUBROTUNDUS, James. 

 CJicetetes subrotnndiis , James (Paleontologist, p. ii, Sept. 14, 1878.) 

 This species is referred to, at this time, for the purpose of correcting 

 a mistake caused by the close resemblance of the surface markings to 

 some species of Chcstetes, and the structure of the interior not being ex- 

 amined and considered, at the time, with sufficient care. On further in- 

 vestigation, there seems no doubt as to its being a sponge. 



GENUS MONTIOULIPORA. D'Orbigny. 

 MoNTicuLiPORA {C/icetetes) whitfieldi, sp. nov. James. 



Compare Chcstetes barrandci, Nicholson (Paleontology of the Province 

 of Ontario, p. 60, fig. xjc) 



The many fragments found of the corallum of this species are very 

 variable in form, and branched very irregularly. Sometimes the branches 

 are quite close to each other, and then an inch or more apart, often 

 rounded off at the ends. Different examples vary in size from ^ to ^ 

 of an inch or more in diameter, with tumid swellings in some cases, 

 and others flattened as if they had been hollow. The calices vary greatly 

 in size and shape, polygonal, oval, circular, pentagonal, and other forms, 

 from 5 to 8 in the space of one line, with more or less of interstitial 

 tubuli. In some cases, groups of calices larger than the average, dis- 

 tributed irregularly over the surface, and, occasionally, groups of from 

 6 to 10 or more of the small tubular openings No monticules, or sur- 

 face elevations observed, but these may occur in other examples. Walls 

 of corallites thin. 



The interior shows the outer walls of the tubes conspicuously wrinkled 

 transversely, and more or less sinuous longitudinally, in cases where 

 specimens have been broken in a longitudinal direction, and the tubes 

 not splintered.* Cut, sHced, polished sections show the wrinkles ob- 

 scurely, if at all, and have a fibrous appearance, with but few irregularly 

 placed tabulas at variable distances apart. The growth of the corallites, 

 commencing in the center, is in a longitudinal direction with an outward 

 inclination, opening on the surface obliquely. 



=■" This feature of wrinkled or rugose tube walls is shown in some other species when similarly 

 fractured. 



