GENUS HOLOCYSTITES. ' 311 



GENUS HOLOCYSTITES (nov. gen.). 

 [Gr. *oXog, totus ; kvgtoq, vesica.] 



Body elongate, subcylindrical, elliptical or subovate, composed of nu- 

 merous ( six or more ) ranges of comparatively large plates, or of alter- 

 nating series of large and small hexagonal or polygonal plates : aper 

 tures 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 regularly alternating series, or sometimes a range of large 

 plates alternating with a range of small ones. There are no indications 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 

 Caryocystites;* but an examination of other specimens has shown that there 

 is no lateral aperture as in the specimens of that genus, and I therefore 

 propose a distinct generic term. 



HOLOCYSTITES CYLINDKICUS. 



Caryocystites cylindricus. Annual Eeport on the Geological Survey of "Wisconsin 



for 1860, p. 23. 1861. 



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



Body elongate obovate or subcylindrical, rounded at top and abruptly con- 

 tracted at base near the junction with the column; basal plates unde- 

 termined. Above the basal plates the first range consists of eight elon- 

 gate 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 attachment. 

 Surface of plates granulose. 



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

 Wisconsin, Vol. i, p. 69. 1862 



