FOSSILS OF THE NIAGARA GROUP. 355 



Several specimens, more or less entire, exhibit the characters here 

 given. While the surface of the plates is coarsely granulose, there is no 

 evidence of ridges or nodes. Some of the specimens show irregularities 

 in the form and proportions of the plates, indicating the possibility of a 

 gradation between this and the following species; but the material I 

 have is not sufiicient to determine this question. 



Formation and LocaKty. — In the limestone at Racine and Waukesha, 

 Wisconsin. 



HOLOCTSTITES ALTERNATUS, HaLL. 



PLATE XII, FIG. 9; PLATE XII a, FIG. 6. 



Caryocystites alternatus, Hall. Ann. Rep. Geolog. Survey Wisconsin for 1860, p. 23. 1861. 



Geology of Wisconsin, T, p. 69. 1862. 



Body extremely elongate, subcylindrical, the greatest diameter above 

 the middle and nearer the apex. Summit irregularly rounded, a 

 little flattened or depressed on the side of the aperture ; base gradu- 

 ally tapering to the summit of the column. The body is composed 

 of twelve ranges of plates varying in size and shape ; in some of 

 the ranges they are large, mostly octagonal, eight in number in 

 each range. In the alternating ranges they are smaller, five or 

 six-sided, and about as many as in the ranges of large plates. Near 

 the summit, and apparently between the eleventh and twelfth 

 ranges from the base, there is a distinct aperture, with another 

 smaller one more nearly on the summit. Surface strongly granulose. 

 These apertures correspond to the mouth and anal aperture as 

 described by Yon Buoh in Caryocystites ; but the lower lateral 

 one, or ovarian aperture, has not been recognized in this or any 

 other species of this genus. 



The specimens of this species are partial casts, but the forms of the 

 plates are fully preserved, and the structure of the body is very dis- 

 tinctly shown. The specimens with alternations of larger and smaller 

 ranges of plates are usually less robust than those where the series are 

 more nearly equal in size. 



Formation and Locality. — In the limestone of Racine, Wisconsin. 



HOLOCYSTITES ABNORMIS, N. S. 

 PLATE XII, FIGS. 7, 8. 



Body subcylindrical, abruptly attenuate below to the short column, com- 

 posed of about eight or nine ranges of plates ; summit rounded ; the 

 principal aperture near the centre is marked by a depression of 



