Missouri Palaeontology. — Rowley. 305 
Figure 19 is a round, rather large stem that has been girt 
about by apparently several colonies of Mmiilopora and has en- 
larged itself greatly about the region of attachment by external 
growth that has enveloped and, doubtless, destroyed the para- 
sites. 
Figures 17 and 18 are swollen stems with pits and depres- 
sions due either to Monilopora or some boring organism. 
One crinoid stem in our possession less than a quarter of an 
inch in length has two girding Moniloporae. 
Conical pits often thickly cover the surface of enlarged 
stem joints and occasionally plates of crinoid bodies, giving 
rise, in the latter case, to warty protuberances, but the origin 
of these pits is as yet unknown to the writer. 
A calyx of a Cactocrimis before us has every plate covered 
by the mouths of small pits. 
It is a little surprising that this Monilopora grew only on 
crinoid stems and nine out of even,- ten of our specimens gird 
Platycrinus stem joints. Evidently there was a preference for 
the stems of the latter genus. 
Two crinoid columns before us are noticeably constricted 
by girding Bryozoa, incrusting the stems at those places. Fig- 
ures II, 16 are of specimens from near the middle of the Lower 
Burlington limestone. The rest are from the top of the Lower 
Burlington, while the collection contains many from the base 
of the Upper Burlington and the top of the Chouteau lime- 
stone (at Fern Glen, Mo.). 
Locality, Louisiana, Mo. 
Orophocrinus stelliformis. 
Fig. 20. Aspect of the ventral side of a natural cast. 
The specimen figured is the only natural cast of this species 
ever found by the writer and shows some interesting features. 
From the central pentagonal opening radiate five bifurcating 
canals with an apparent semicircular canal about the center. 
The ten elongate, spiracular slits appear as elongate, ellip- 
tical elevations, the hydrospires being faintly outlined only near 
the distal ends of the ambulacra. The anal opening also ap- 
pears as a slight elevation between two ambulacra. 
The specirrien is from a chert nodule of the Lower Bur- 
lington limestone, Pratt's quarry, Louisiana, Mo. 
