LECANOCRINIDAE l8l 



Impinnata with no iBr along with Lecanocrinus and Ichthyocrimts, following Angelin whose 

 figures of apparently perfect specimens showed neither interbrachials nor any space for their 

 accommodation. In fact the principal figures of both his species are restorations and incor- 

 rect, especially that of the type species, P. scrobiculaUts (Icon. Crin. Suec, pi. 15, figs. 10, 

 11). Instead of having the rays rather closely abutting as in his figures II, 12 and 14 on 

 plate 15, the first primibrach does not fill the distal face of the radial, but leaves shoulders on 

 either side, above which there is a considerable space between the rays. One of the specimens 

 in the Riks Museum examined by Mr. Liljevall shows at the inner margin of this space dis- 

 tinct traces of the articulation of small plates, both in the regular interbrachial areas and 

 above the anal plate (PI. XI, figs, gc, d). 



After receiving these drawings, and having seen the nearly perfect specimen in the 

 British Museum- with its wide spaces between the rays above the shoulders of the radials 

 (PL XII, figs. 10a, b), I concluded that these large interbrachial spaces must have been occu- 

 pied by an integument of small plates, although they had never been seen, and upon that 

 ground assigned the genus to a definite place in the group now called Sagenocrinidae. 1 This 

 interpretation of the structure was soon afterward definitely confirmed in an unexpected 

 quarter. Up to that time, with the exception of an imperfect specimen described by Weller 

 from the Niagaran of Chicago, our knowledge of the genus was derived from the few 

 specimens found in Gotland and England. It was. therefore with no little satisfaction that I 

 found among the collections made for me by Pate from the Niagaran limestone of western 

 Tennessee a number of fine specimens of Pycnosaccus, some of them having the interbrachial 

 areas perfectly filled with small plates. The structure of these areas is delicate and fragile as 

 compared with the massive calyx plates and generally robust arms, but it is perfectly pre- 

 served in place in several specimens (PI. XII, figs. 20, b, 30, b), and in one of them some of 

 the small plates are surmounted by sharp nodes (figs. 3a, b). 



Owing to the absence of definite plates in the interbrachial areas there is a distinct line of 

 demarcation between calyx and arms, which gives to this form an entirely different habitus 

 from any of the preceding, and indeed from most of those in the entire group. Thus under- 

 stood, the genus stands widely distinct from those with which it has been associated, the only 

 near approaches to it being the anomalous genus Cholocrinus, which has a closely similar 

 calyx but an entirely different brachial structure, and its Carboniferous successor, Niptero- 

 crinus. Even with the calyx alone it is readily distinguished from Lecanocrinus by the charac- 

 ter of the radial facets. As in that genus there is a tendency to irregularity in the number of 

 primibrachs, which is utilized as a specific character although not very reliable or sharply 

 defined. 



The type species, P. scr'obiculatus, was described from the calyx alone without any arms 

 or brachials attached, and Angelin's subsequent figure (pi. 15, fig. 11) being as already stated 

 an imaginary restoration as to the arms, was without authority in representing it with a 

 single primibrach. The species is recognized in typical specimens, mostly from Klintberg, 

 horizon f, by its prominent ridges on the calyx plates. On one of these Mr. Liljevall found a 

 primibrach in place on two of the rays (PI. XI, figs. 6a, b) but on neither is it an axillary, thus 

 showing that the species may have more than one primibrach. He also found in the Riks 

 Museum a well-marked but unusually large specimen from Wisby, probably of the same 

 horizon, with three rays partly intact, having two primibrachs in two of them and one in the 

 third (PI. XI, fig. 7). From these two specimens it may be concluded that two primibrachs 

 is the general rule in this species. This is reinforced by the peculiar condition of these parts 

 in P. nodulosus , a smaller Gotland form scarcely distinguishable from the "'former. Out of 

 three specimens with arms one has a single primibrach all around, but the other two have in 



'Journal of Geology, vol. 14, 1906, pp. 484, 517. 



