312 EIGHTEENTH REPORT ON THE STATE CABINET. 



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 

 sufficient to satisfactorily determine this question. 



Formation and locality. In the limestone at Racine and Waukesha, 

 Wisconsin. 



HOLOCYSTITES ALTERNATUS. 



Caryocystites alternatus : Hall, Report of Progress Geol. Survey of "Wisconsin for 



1860, p. 23. 1861. 



* " Geology of Wisconsin, Vol. i, p. 69. 1862. 



Body extremely elongate, subcylindrical, the greatest diameter above the 

 middle and nearer the apex. Summit irregularly rounded, a little flat- 

 tened or depressed on the side of the aperture ; base gradually 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 Von Buch in Caryocystites ; but the lower lateral one, or ova- 

 rian 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 distinctly 



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.). 



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 the 

 surface. In the third range from the base, two or more of the large plates 

 are surrounded by smaller ones ; but the four ranges of plates below the 

 dome are large plates of nearly equal size and equal length and breadth. 

 Surface of plates granulose. 



