354 REPORT ON THE STATE CABINET. 



plates; apertures at or near the summit, one of them central or 

 subcentral, the other eccentric. Supported on a short pedicel. 

 Sessile arms none ; free arms unknown ; no evidence of pectinated 

 rhombs. 



The specimens referred to this genus are generally composed of large 

 plates in pretty regular alternating series, or sometimes a range of 

 large plates alternating with a range of small ones. There are no indica- 

 tions of sessile arms as in Gomphocystites ; though there may have been 

 free arms around the central aperture of the summit. The surface of the 

 plates is strongly granulose, and sometimes marked by ridges and central 

 nodes. 



I had originally referred these forms with some doubt to the genus 

 Cartocistites ;* but an examination of other specimens has shown that 

 there is no latei'al apertm^e as in the species of that genus, and I 

 therefore propose a distinct generic term. 



HOLOCTSTITES CYLINDRICUS, HaLL. 



PLATE XII, FIGS. 4, 5; PLATE XII a, FIGS. 7, 8. 



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



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



Body elongate obovate or subcylindrical, rounded at top and abruptly 

 contracted at base near the junction with the column ; basal plates 

 undetermined. Above the basal plates the first range consists of 

 eight elongate hexagonal plates, their length once and a half their 

 greatest width, gradually expanding in width from below upwards ; 

 these are succeeded by a second, third, fourth and fifth range of 

 eight plates in each, all somewhat regularly hexagonal, their length 

 a little greater than their width. Of these, the fourth range is 

 usually the widest, situated at a little more than one-third the 

 length of the body from the summit, and at the point of greatest 

 diameter. In the sixth range above the basal, the plates are 

 much smaller than the others, and narrower at the upper end. 

 Alternating with these last, is a seventh range of smaller plates, 

 surrounding those of the summit, and enclosing the summit openings. 

 Column small, round, rapidly tapering below the point of attach- 

 ment. Surface of plates granulose. 



* Annual Geological Report of Wisconsin for 1860, published 1861 ; and Geology of Wisconsin, 

 Vol. i, p. 69. 1862. 



