172 Cincinnati Society of Natural History. 
peculiarities. The form above the tertiary radials is wholly different 
from that of any other described species. 
Saccocrinus NEcIS, W. and M. 
Plate IV., fig. 3, azygous side of a medium sized specimen; fig. 3a, view, showing a good 
vault ofa slightly compressed specimen. 
( Megistocrinus necis, Winchell and Marcy, 1865, Mem. Bost. Soc. 
Nat. Hist. ) 
This species is variable in form and size. Of twenty-two specimens 
examined, the smallest has a length of 1 4-10 inches, and a diameter 
of 1 15-100 inches, and the largest has a length of 2 4- ak inches, and a | 
diameter of 2 inches. 
Body somewhat turbinate in outline; pointed below; expanding to 
the third radial; abrubtly contracting to the arm bases; tumid in the 
middle anterior region, and flattened or depressed in the upper an- 
terior part; and sometimes having a slightly pentagonal outline when 
seen from below. 
Basals.—Basals, hexagonal, of moderate size, and forming an 
acutely pointed cup. 
Radials.—First radials large, longer than wide, three hexavonen two 
pentagonal, the lower lateral sides being the longer ones. Second 
radials smaller, hexagonal, and longer than wide. Third radials, 
heptagonal, longer than wide, and supporting upon the two upper 
sloping sides the secondary radials. There are two heptagonal 
secondary radials in each series, the first one of which is about two 
thirds as large as the third radial, and the second about one third as 
large. The latter are surmounted by single tertiary radials, from 
which the brachial series arise. 
Interradials.—Regular interradials, twelve. The first is hexagonal, 
and of about the same size as the second radials. It is succeeded by 
five pairs and one intervening plate, at the region of the greatest body 
expansion. Above these there are, apparently, four interbrachial 
plates. 
Intersecondary radials. — The first intersecondary radials are 
pentagonal or hexagonal, and a little smaller than the second second- 
ary radials. The hexagonal ones are succeeded by two small inter- 
secondary radials, and above these, there are, apparently, four inter- 
brachials. The pentagonal ones are succeeded by a single inter- 
secondary radial, above which there are interbrachials, 
Azygous interradials.—There are twenty-five or twenty-six azygous 
