ART. 18 THE CRTNOID GEISTUS APIOCRTNUS^ — SPRINGER 3 



]imnin<>- iiiAvard from the periphery to a smooth riii**; siirromiding- 

 the himen, about one-third the diameter of the cohimiial and flush 

 with sthe adjacent surface; this is seen in several specimens, and is 

 evidently a constant character, with perhaps some variation in rela- 

 tive diameter. 



In the structure of the joint-face may be seen the decisive differ- 

 ence between this genus and Pentacnnus, Isocrinus, or BalcunocrinuSy 

 the other forms which might be encountered in rocks of the same age. 

 In these the joint-face is divided into five petaloid sectors differing 

 among the genera, the first two having short crenelations at the mar- 

 gin of the sectors, and the last having them only at the periphery of 

 the stem. In Apiocrinu!^ there are no sectors, and the striae extend 

 directly inward for about one-third to two-fifths the diameter of 

 the joint, or perhaps sometimes all the Avay to the lumen. For con- 

 venience of comparison with the Apiocrinus joint-face, and also to 

 facilitate identification of fragments that are likely to be found, I 

 am giving characteristic figures of the other two tj^pes (pi. 1, figs. 

 8, 9, 10, 11). The smooth ring surrounding the lumen is a marked 

 character in our species, occupying about one-third the diameter of 

 the joint, probably varying in different parts of the stem; it is but 

 little, if any, sunken below the general surface of the joint, and the 

 striae in some cases pass over it. 



Among European species comparison may be made with Apio- 

 crinus elegans (Defrance), which is of a very similar type to our 

 species, having usually less curvature to the sides of the expanded 

 stem than in such characteristic species as A. parkinsoni and A. 

 roissyanus. Ajnocrinus elegans was described b}^ Defrance in 

 1819 * as Astropoda, and in 1839 was referred by D'Orbigny to 

 Apiocrinus.^ The species is Avidely distributed, and occurs at many 

 localities in France, especially in tlie districts of Calvados, Cote 

 d'Or, Nievre, etc. It has been thoroughh^ described and figured by 

 De Loriol,*' from whom I am giving copies of his figures 1, 4, and 6 

 of plate 34, shoAving the contour of stem and calyx, and figures 4, 

 4&, 4<? of plate 35, giving details of the joint-face. 



In relative proportions of the corresponding parts there is little 

 difference between our species and this. In the 5 columnals of ours 

 the spread in diameter is as 1 to 1.4; in De Loriol's figures of A. 

 elegans on plate 34 for the same number of columnals the spread in 

 figure 4 is as 1 to 1.5, and in figure 6 as 1 to 1.6. The joint-face as 

 shown by figures 4, 46' of plate 35, has a somewhat less number of 

 striae, about 48, and a similar smooth median ring, which is i-ola- 

 ti^ely larger and distinctly sunken. This smooth inner ring sur- 



♦ Diet, des Sci. Nat., vol. 14, p. 468. 



i^Hist. Nat. des Crlnoldes, p. 29, pi. 5, figs. 9-15. 



• Criuoidesf de la Fiance, vol. 2. pt. 1, 1883, p. 240, pis. 34, 35. 



