226 Twenty-third Report ox the State Cabinet. 



the addition of several other corals, among which is a new species of 

 Acervularia and two species of Smithia described in these pages. 



From the assemblage of fossils found at these two localities (Rock- 

 ford and Ilackberry), we are inclined to consider these beds as equiva 

 lents of the Chemung group of Xew York. 



DESCRIPTIOXS OF XEW SPECIES. 



Genus — STROMATOPORA Gold. 

 Stromatopoka erratic a n. sp. 

 Specimens growing in strong, irregular, convex or hemispherical 

 masses, six or eight inches in diameter, becoming extremely rough and 

 irregularly laminated on weathering, but in a vertical section or fresh 

 fracture showing a remarkable regularity of structure, with the excep- 

 tion of a slight alternation in the density, occurriiig at intervals of from 

 an eighth to a sixth of an inch. Yertical columns much thicker than 

 the spaces between, five to seven in the space of a tenth of an inch, 

 moderately diverging upward, unequal in strength and frequently 

 coalescing. Horizontal filaments appearing as continuous in a section, 

 from six to eight in a tenth of an inch, much thicker than the inter- 

 spaces, and expanding at tlieir junction with the vertical column. 



Weathered specimens present a somewhat coarsely shagreen-like 

 surface, with occasional distant, slightly elevated patches of greater 

 density, or of a madreporiform structure. 



Fo'i'mation and locality. In the coralline beds, and found abund- 

 antly in detached specimens over the surface and along the banks of 

 streams at Waterloo, Iowa. 



Stromatopora EXP ansa n. sp. 



Plate 9, flg. 1. 



Specimens in large expanded lamellar masses, sometimes of many 

 feet in extent, with a slightly uneven or undulating surface, which is 

 covered with broad, low prominences, distant from center to center 

 three-eighths to one-half of an inch. In a vertical section the columns 

 are distant from each other a little more than their own diameter, and 

 are from six to seven in number in the space of a tenth of an inch. 

 The horizontal layers are more closely arranged, becoming crowded at 

 regular intervals of about a sixth of an inch, and averaging from ten to 

 thirteen in the space of a tenth of an inch. 



This crowding of the horizontal plates at intervals gives to the mass, 

 when broken, a coarsely laminated character. When viewed on the 

 surface it presents the ajipearanco of minntc, generally five-pointed, 

 stellate forms, from the vertical columns being connected by the minute 

 lateral processes, which form and represent the horizontal plates as seen 

 in the vertical section. 



