OWEN AND SHUMARD'S FOSSIL CRINOIDEA. 65 



' Among a number of specimens of Fentremites florealis, (Say,) procured by Mr. J. 

 Evans at Chester, Illinois, we have found one, in which the arms still remain 

 attached, and lie folded in the ambulacral spaces. These arms are extremely 

 delicate, and originate at the so-called pores of the ambulacra. They are composed 

 of small plates arranged in longitudinal series, as in the true crinoids. None of them 

 bifurcate, and we have not been able to observe any traces of tentaculae. In the 

 same specimen the five apertures at the summit are completely closed by a conical 

 abdominal integument, made up of small microscopic pentagonal plates. 



Pentremites melo. (New sp.) 

 Fig. 14, a, h, c. 



The form of this pentremite is globular, sometimes slightly elongated, and the 

 surface is ornamented with minute granulae, very regularly arranged in longitudinal 

 rows as in the P. Norwoodii. 



Basal plate small, pentagonal, flat or slightly concave, composed of three pieces, 

 two are broad pentagonal and one is rhombic. The articulating surface for the 

 column, which is round and equal to one-half the diameter of the plate, is finely 

 striated on the margin, and exhibits a minute central perforation. The external 

 edges of the plate are slightly concave to accommodate the inferior rounded edges of 

 the perisomic plates, (costals of Miller.) 



These latter are of an elliptical form, convex, and project inferiorly a little below 

 the plane of the basal plate, while their surnmits are truncated on both sides of the 

 ambulacra for articulating with the superior plates. Their union is strongly marked 

 by a deeply indented longitudinal furrow. The ambulacra are narrow and widen 

 slightly from below upwards, they commence from a half to three quarters of a line 

 above the basal edge of the plates and are continued a little beyond their superior 

 margins, being more deeply inserted into the ambulacral gutter superiorly than 

 inferiorly. The ambulacra are composed of numerous small plates arranged as in 

 the P. Norwoodii, these are marked on the edges by fine striae, which are perceptible 

 only by the aid of a good lens. 



Superior plates small, elongated, symmetrical, composed at the base of a truncated 

 triangle, surmounted by an irregular hexagon. The inferior lateral edges of the 

 hexagon in four of these plates are notched, so that when united to the contiguous 

 ambulacra eight pores are formed, surrounding the summit. The fifth superior 

 plate is perforated with an oval opening — the vent — which is much larger than the 

 above mentioned pores. 



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