INSERTAE SEDIS 447 



peculiar lines of growth. Doubtless when very young these were all attached to other 

 objects by the lower ends of the basals, which were obscured in the process of attachment, 

 and when free became totally changed by secondary growth, in which condition all signs of 

 suture lines are obliterated. Many small specimens are found attached to hard objects, 

 either singly or in clusters, sometimes half a dozen on a single shell. Various forms of these 

 bases are shown by Hall's figures in Volume III, Pal. N. Y. plate 87. 



But along with these are a considerable number ranging from small to full adult size 

 which have a broad, flat, encrusting base for fixation, wonderfully like the mode of attach- 

 ment of the existing genus Holopus. Specimens of this class have a different aspect other- 

 wise from those with rounded base, and upon assembling the material it became evident that 

 the two types are specifically distinct, the attached form having uniformly much shorter 

 rays. Excluding the very young individuals, in which the primary brachials cannot be 

 counted because they infold before the first bifurcation, there are 63 specimens from small 

 to maximum size with one or more of the rays preserved, many of them entirely complete; 

 of these 42 are free as figured by Hall on plate 87, figure 10, and all of them agree with his 

 description of E. sacculus in having 10 or 12 (or more) very short primibrachs. Of the 

 other 21 specimens with attached base, 16 have 5 IBr in nearly all the rays, and the remain- 

 ing five have from 5 to 7. Several sessile specimens have 10 IBr, but they are all small ones 

 which might have become free with age. Thus without exception in the adult the sessile 

 form has 5 (or at the most 6 or 7) IBr, and the free floaters 10 or more, — a constancy of 

 characters quite sufficient to separate the species. There are numerous detached bases of the 

 sessile form, which differ markedly from the others by their much thinner walls and broader 

 cavity. Both forms are well illustrated on plate 40 of the volume on the Lower Devonian, 

 of the Maryland Geological Survey, 1913, of which figures 10, 11, 12 show the free form, 

 E. sacculus, with its 10 or more IBr, while figures 7, 8, 9 represent the sessile form with 

 5 IBr, for which I propose the name Edriocrinus holopoides. The original of figures 7-9, 

 which I have refigured as the type specimen (PL LXXVI, figs. 22a, b), is in an unusually 

 good state of preservation, the attachment having been to a smooth object; and it distinctly 

 shows upon the lower surface of the encrusting base the course of the original suture lines 

 of the 4 basal plates, as appears by the photographic figure, 22b. 



Both of these forms have the same large anal plate ; very broad arms, branching, and 

 strongly curving distally, with a distinct, rather large ventral furrow or food groove. The 

 preservation in the coarse sandstone matrix has been impaired by chemical action due to the 

 presence of iron oxide, so that finer structures are obscured ; thus we do not know how the 

 food groove was covered, nor whether pinnules were present. There might have been short, 

 stout appendages as in Holopus, but no evidence of them is visible in the fossils. 



The outstanding fact in regard to this singular form is the complete absence of a stem, 

 and its remarkable superficial resemblance to Holopus, from which it differs broadly in its 

 bilateral symmetry due to the presence of the large anal plate, and in the probable absence of 

 pinnules. Both are of a littoral or circum-littoral habitat. Holopus occurs on rocks or 

 corals within a few fathoms depth, while the Oriskany sandstone in which the largest species 

 of Edriocrinus occur is recognized as a littoral deposit. The time interval between them is a 

 tremendous one, perhaps partially bridged by Eugeniacrinus and its congeners from the 

 Jurassic to the' Cretaceous, and by Cyathidium from Cretaceous to Tertiary. The two 

 doubtless represent parallel modifications of independent stocks, resulting from their 

 encounter with similar physical conditions. There is no evident connection between Edrio- 

 crinus and any other Devonian or pre-Devonian form, unless the newly discovered fact of 

 the 4 basals may suggest some remote relation to the Melocrinidea. The monocyclic base 

 and rigid construction of the calyx are facts which negative a connection with the Flexi- 

 bilia as now limited. 



