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ART. VIII. — Notice of Fossils from the Carboniferous Series of the Western States, 

 belonging to the genera Spirifer, Bellerophon, Pleurotomaria, Macrocheilus, 

 Natica, and Loxonema, with descriptions of eight new characteristic species. By 

 Joseph G. Norwood and Henry Pratten, of the Illinois Geological Survey. 



SPIRIFER. 



S. spinosus, no&.— Plate IX. fig. 1, a, b, c, d. 



Shell rather small. Both valves very convex. The dorsal valve bears five or six 

 rounded ribs on each side of the sinus. The ventral valve has four, and sometimes 

 five, similar ribs on each side the central lobe. The lobe itself resembles a large rib, 

 being only about double the size of those next to it on each side. The other ribs 

 gradually diminish in size as they approach the cardinal border. They are covered 

 with large and deep but irregular striae of growth, which are most numerous near the 

 margin. Besides these large imbricated striae some of the most perfect specimens are 

 beautifully marked with finer concentric striae, visible only by the aid of a lens. 

 The surface of the shell is irregularly covered with short, hollow spines, projecting at 

 nearly right angles from their bases. On all the specimens yet met with the spines 

 are broken, the longest fragments measuring about one-sixteenth of an inch. In 

 addition to these spines, the whole shell, including the cardinal area, is covered with 

 minute granules. Where these are rubbed off there is the appearance of small open- 

 ings into the shell, giving it the aspect, somewhat, of being covered with a minute 

 coral. Cardinal area, triangular ; high ; a little shorter than the greatest breadth of 

 the shell, and having sharp edges on the ventral valve only. The median slit is large 

 and open, and occupies about one third of the space left free from the encroachment 

 of the ribs of the dorsal valve. 



Dimensions. — Length, six tenths of an inch ; breadth, eight tenths. 

 Comparisons and Differences. — This shell has nearly the form of the S. octoplicatus, 

 of Sowerby, but diners in having fewer ribs ; in the sinus of the dorsal valve being 

 wide and rounded at its bottom ; and also in all its ribs being rounded. When the 

 epidermis is well preserved, the spines with which it is covered will readily distinguish 

 it from all other species. 



Geological Position and Localities. — This species occurs near the top of the mountain 

 limestone, associated with Pentremites sulcatus, piriformis, and florealis, Prodwctus 



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