500 PALEONTOLOGY OF ILLINOIS. 



DlCHOTRYPA ELEGANS UMch. 

 PI. LXXVI, fig. 8-8d. 



Zoarium a more or less undulating frond, or palmate expan- 

 sion, several cm. in width and heighth, 1.5 to 3 mm. in thick- 

 ness; with the lateral margins sub-acute and non-poriferous. 

 Lower portion of zoarium perfectly smooth, being covered by 

 a dense cortical substance. Above this the surface is marked 

 with circular or sub-stellate solid maculae, which sometimes 

 crown the summit of low, broad, rounded monticules. Maculae 

 more or less regularly arranged, about three mm. apart; with 

 the apertures immediately surrounding them, slightly larger 

 than the others: Apertures a little oblique, circular, from 0.11 

 to 0.16 mm. in diameter, with elevated peristome, usually high- 

 est on one side, arranged in regular bent diagonally intersecting 

 series, about once and a half their diameter apart, eight of those 

 in the intermacular spaces in three mm. Interspaces sometimes 

 slightly concave, generally with a faint ridge or ridges, forming 

 sub-polygonal depressed areas around the zocecia apertures. In- 

 ternal structure similar to that of the type of the genus, but 

 the primitive portion of the zooecia is not regular in its form. 

 Just below the surface the inter-zooecial spaces are more dis- 

 tinctly marked with the intermittent concentric lines. 



This species differs from D. intermedia and D. expatiata, by 

 the smooth lower portion of the zoarium, the sub-stellate mac- 

 ulae, and the less strongly developed lunarium. From D. flabel- 

 lum, Rominger, and D. lyroides, by its different growth. 



Position and locality: St. Louis group; Elizabethtown, Ky.; 

 Jersey and Monroe Co.'s, 111. 



DlCHOTRYPA INTERMEDIA Ulrich. 



PI. LXXVI, fig. 9-9c. 



Zoarium sub-ramose, consisting of an explanate frond 

 which throws off at intervals similar fronds, till there is pro- 

 duced somewhat the appearance of several successive fans grow- 

 ing from one another; entire height eight or more cm., width 

 varying from one to three cm.; thickness rarely exceeding 1.5 



