278 SMITHSONIAN INSTITUTION 



IBB small, covered by column. BB small, not wholly exposed, visible as 

 triangles beyond the column in side view; relatively larger in young specimens, 

 which are also more elongate in general dimensions. Brachials obtusely rounded 

 into a low median ridge, increasing in angularity upward, and well-marked in 

 the upper ray divisions; median elevation of rays more apparent in flattened 

 specimens, and scarcely observable at the lower part in rotund ones. IIBr gen- 

 erally 4, sometimes 3. Average height to width of IBr, about 1 to 2; of IIBr, 

 about 1 to 3. Column long, proximally enlarged, expanding rapidly for a few 

 ossicles to the diameter of the base; below this it is relatively small, diminishing 

 in a medium-sized specimen from 5 mm. to 3 mm. continuing thus to near the 

 distal end where it slightly enlarges. It is smooth, composed of nearly uniform 

 columnals, and is at least 23 cm. in length. 



Conrad's description of this species, like many of the earlier descriptions in this group, 

 was short, but it contained one important point ; it reads, " there is much resemblance in the 

 markings of this fossil to the scales of a fish, whence the generic name is derived." 1 This 

 feature, which he also gives as a generic character, is found in most of the species, but it 

 is particularly well-marked in this, and distinguishes it from /. subangularis as usually found 

 in the Waldron shales. It is illustrated on Plate XXXIII, figure 3d, where it will be seen that 

 the plates do not actually overlap, but the upper transverse margin is rather abruptly raised 

 just at the suture line, giving somewhat that appearance. In some specimens this projection 

 is quite sharp and prominent, and can be easily felt by running the finger nail downward 

 against the sharp little steps. In the English species /. phillipsiamis this transverse elevation 

 is considerably higher, and involves a larger portion of the plate (PI. XXXVI, fig. 14c). 



Conrad's figure {op. cit., pi. 15, fig. 16) leaves no doubt that it represents the species 

 found in the Niagaran shales at Lockport, New York, but if we did not have other specimens 

 in similar condition for comparison it would be misleading in several particulars. It is made 

 from a flattened specimen, and the sides appear as if convex almost from the stem. The 

 base and small part of the stem shown are too small, doubtless because not perfectly cleaned 

 from the matrix. In a normal specimen the base is fairly broad, and the side of the calyx 

 expands upward with a slight inward or concave curve, which is soon reversed into a broad 

 convex outline extending to the level where the arms are folded inward — the zone of greatest 

 width being a little over half way up, and considerably above the level where the curve 

 changes. This is well shown in such rounded specimens as Plate XXXIII, figures 3, 4. But 

 with a flattened specimen the side outline is very different ; the whole effect of the reversed 

 curve is lost and the calyx appears convex from the base up, as in Conrad's figure. In order 

 to show the result of such flattening I have given, along with the figures of several such 

 specimens, their curved outlines obtained by calculating the diameter from accurate measure- 

 ments at four zones (PI. XXXIII, figs. 10b, lib, 12b, 13c). 



These figures show what a substantial uniformity there is in the contour of the speci- 

 mens, however much altered by pressure. In young specimens the characteristic figure has 

 not been fully attained; they are more ovoid, and also more elongate (figs. 5, 6). The 

 specimens vary somewhat in the prominence of the median radial ridge in the lower part, 

 where it is often quite obscure, especially on rotund specimens ; but it is always distinct in 

 the higher parts of the rays, where it becomes quite angular. The column is rather small for 

 the size of the crown except at the calyx where it is flush with the base, and tapers very 

 rapidly for a few thin columnals to little more than half that diameter ; thence it continues 



1 Jour. Acad. Sci. Philadelphia, vol. 8, 1842, p. 279. 



