244 
PALJEONTOLOGY OF NEW-YORK. 
plates, and the larger tubercles sometimes forming straight ridges from the centre to the angles 
of the plates. 
This exquisitely beautiful little fossil is from the collection of Col. Jewett of Lorhport, and 
was found associated with the preceding species, and with Caryocrimis ornatus. This is much 
smaller than Callocystites, and is very conspicuously different in the form of the plates and 
the number of those in the second series, as well as in the position of the higher pectinated 
apertures. The arms are but four, and very obviously consist of an anterior and posterior pair, 
which are united at their bases. The character of the shallow groove in which these arms rest, 
and the groove or avenue in the arms themselves, is precisely similar to the preceding genus. 
The little ossicula partially filling this groove are not perfectly preserved in that one, though 
there remains sufficient to prove their existence originally. In the present form there is an oral 
orifice near the summit, and a minute anal pore below ; while in Callocystites the mouth is 
smaller, and the anal orifice proportionally larger, and there is a distinct tubercle on one side 
of the mouth, which does not appear in this one. 
The body, in a well preserved specimen, appears to be slightly compressed laterally ; though 
in another specimen, apparently in its natural condition, there is no perceptible difference in the 
two diameters. The groove in which the arms lie is more deeply impressed near the summit 
than in the lower part, and distinctly divides the body into four lobes. Modifications of the 
form, to some extent, take place from the introduction of supernumerary plates as in the crinoids 
proper. This also modifies the form of the adjoining plates, as in the example fig. 5, where the 
introduction of a quadrangular plate between the first and second series ha% truncated an angle 
of one of the pentagonal basal plates, and changed the form of one, and altered the relative 
position of the other adjoining plate, of the two succeeding ones of the second series. Modifi¬ 
cations in the form, and subdivision of plates in the third and fourth series, appear not to be 
uncommon in this species. 
The largest specimens seen reach the size of the figures on Plate 51, though others are 
smaller. 
Fig. 1. The posterior side, showing the ovarian aperture, the shallow groove in which the arms 
are lodged, and the base of the larger tentaculum. 
Fig. 2. The left side, showing the pectinated apertures and arrangement of plates on that side. 
Fig. 3. The right side, showing the pectinated apertures and the protruding plates of the ovarian 
pyramid. The plates of one of the arms remain, retaining the minute ossicula, which 
are shown diverging into the lobes of the groove to the base of the tentacula. 
Fig. 4. The anterior side, showing the pectinated apertures at the base, the grooves for the 
anterior pair of arms, and the base of the large tentaculum at the summit. 
Fig. 5. Diagram showing the structure of one specimen having an intercalated quadrangular 
plate between the first and second series of plates. 
Fig. 6. Diagram of the structure of another specimen, where there are only the usual number 
of plates in the first and second series. One plate of the third series, over the ovarian 
aperture, is divided into three distinct plates. Between the plates bearing the pec- 
