CRINOID GENUS SCYPHOCRINUS 31 



figure 1, which gives the correct contour and proportions of a full-sized indi- 

 vidual if undistorted by pressure. The magnificent crown shown by the photo- 

 graph (PL III, fig. 1), reduced to two-thirds natural size in order to come 

 within the limits of the plate, has the calyx almost rotund, and its surface 

 ornament in perfect condition. Plate II shows two fine crowns with stems 

 attached, natural size, exhibiting almost every one of the different varieties 

 of plate sculpturing. 



The surface of the plates to the level of the upper primibrachs, which are 

 all low-convex and thin, is conspicuously marked by sharp, rather low ridges 

 or costse, radiating in parallel sets of five or six from plate to plate, crossing 

 each sutural face at right angles, forming triangular or rhombic striated areas 

 (PI. V, fig. 1). Above this the costae progressively coalesce through various 

 stages to a single narrow ridge, or until they become merely a broad convex 

 band; or they may sometimes disappear altogether. Between these parallel 

 sets, or single ridges — that is, at the angles of the plates — there are depressed 

 areas, or pits, which increase in depth and size concurrently with the coales- 

 cence of the costae. These various stages of the ridges and pits produce in the in- 

 terbrachial areas a stellate, reticulate, corrugated, banded, or smooth surface — - 

 sometimes two or more of these kinds of sculpturing appearing in the same 

 specimen. If the pits enlarge about equally, and the single coalesced ridge 

 remains narrow, the plates will have a more or less stelliform appearance 

 (PI. Ill, figs. 1 and 3) ; if the ridges become about equally broad, a network is 

 produced (PI. Ill, fig. 4) ; if the pits at the upper and lower angles are most 

 enlarged, while the ridges develop chiefly in a transverse direction, the result 

 will be a series of conspicuous, downwardly curved, rope-like bands traversing 

 the space between the rays (PL II, figs. 1 and 2). The condition of wear at the 

 surface of the plates during fossilization, or perhaps in life, sometimes exposing 

 subsurface channels, has often much to do with the appearance of the sculptur- 

 ing. Occasionally the sharp costae on the lower plates tend to become inter- 

 rupted, leading to rows of fine granular pustules, on which Waagen and Jahn 

 based their species 5". decoratus. 



The number of secundibrachs is about 18 to 20, with little variation, being 

 more regular here than it appears in the figures of Waagen and Jahn, which 

 show variations of 15 to 25, some of them perhaps due to inaccurate observa- 

 tion or drawing. In this character the species differs from all the Tennessee 

 species, which rarely have more than 15 secundibrachs. The lower secundi- 

 brachs are of about equal width and length ; they diminish in length until those 

 next to the axillary are about five or six times as wide as long, average length 

 at this level being about 1 mm. From about the sixth or seventh secundibrach 

 they gradually become wedge-form, the wider margin supporting a pinnule 

 which also abuts more or less on the short margin of the alternate brachial; 



