314 EIGHTEENTH REPORT ON THE STATE CABINET. 



A specimen of one incli and three-fourths in length, cand imperfect at base, 

 shows ten ranges of plates between the broken lower margin and the 

 summit aperture. The greatest diameter of the same individual is one 

 inch and a half, while it is about half an inch in diameter where broken 

 off, and there have probably been two or three ranges of plates below 

 that point. A section below the summit is very broadly elliptical, and this 

 has probably been the original form. 



This species differs from H. scutellatus in being a more robust form, 

 with less elongate base, and with plates larger, more equal in size, and 

 prominent in the middle; while the larger plates in that species have cen- 

 tral nodes from a nearly flat surface. 



Formation and locality. In the limestone of the Niagara group at 

 Waukesha, Wisconsin. 



HOLOCYSTITES SCUTELLATUS (n. s.). 



General form of body ovoid ventricose, abruptly attenuate below, and 

 swelling above into an ovate outline ; composed of twelve or more ranges 

 of plates which are somewhat irregularly disposed, there being in the 

 upper part a distinct arrangement of one large polygonal plate surrounded 

 by smaller ones, this large plate having a node in the centre. The sum- 

 mit is broadly rounded, with evidence of one large subcentral aperture, 

 and a depression indicating a second aperture. Surface of plates 

 strongly granulose. 



The ventricose ovate form and abruptly attenuate base are distinguishing 

 features of this species. Though the H. cylindrius sometimes assumes 

 an ovate form with attenuate base, yet the species here described has a 

 much larger number of plates, which are differently disposed. 

 Formation and locality. In limestone of the age of the Niagara group 



at Waukesha, Wisconsin. 



GENUS APIOCYSTITES (Forbes). 

 APIOCYSTITES IMAGO (n. s.). 



Body irregularly elliptical, about three-fifths as wide as long, a little 

 larger above than below the middle. Basal plates occupying more than 

 one-fourth of the entire height of the body. Second range consisting of 

 five large plates. In the third range the plates are about half the size 

 of those of the second range. The fourth range consists of at least six 

 plates ; the two over the ovarian aperture are smaller than the others. 

 The fifth range consists of six plates of smaller size than the others and 

 of a pentagonal form, the upper margins being determined by the num- 

 ber of apicial plates, which are unknown. 



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