INDIANA PALAEONTOLOGY. J66. 



MEGISTOCRINUS EXPANSUS, M. ife G., Rowley. 



Plate 48. Figs 7, 8, 9, 13, U, 15. 



The larger of our two specimens is a fine one and shows well the plate su- 

 tures. It differs somewhat from Miller & Gurley's species in that the dorsal 

 plates are slightly concave against flat in that species and the periphery be- 

 tween the arm lobes and especially in the anal region has the appearance of 

 having been pinched into a ridge. The same feature is seen on figures 8, 9, 10, 

 plate xxiv,'part viii, Contribution to Indiana Palaeontology. 



The five ventral spines are well developed on this specimen. Anal tube 

 rather strong and excentric. 



There are sixteen arms and the peculiar fine linear ornamentation charac- 

 teristic of the M. depressus group. 



The small specimen figured is hardly concave at the base, has sixteen arms, 

 five ventral spines and with the lines of ornamentation beautifully preserved. 

 Contrary to the larger specimen the plates are flat (not concave) or slightly 

 C(mvex in the radial ring. 



The ornamentation consists of short parallel lines crossing the sutures and 

 extending toward the plate centers, which latter are covered by short lines or 

 granules. Toward the periphery the^lines become more or less distorted. This 

 ornamentation is almost microscopic, and we venture to say here, that every 

 species of flat and so-called smooth-plated Megistocrinus from the Upper De- 

 vonian beds of Indiana, possess this ornamentation when well preserved. We 

 have seen it on several so-called species. It will be also noticed that the lat- 

 eral diameter passing through the anal region, is longer than any other lateral 

 diameter in the sixteen armed, smooth (?) species. 



There is something suggestive in these observations that might be used 

 profitably in a needed revision of the genus. 



Both of our specimens are from the Upper Devonian beds of Clark county, 

 Indiana. 



HOLOCYSTI^ PAPULOSUS? M. & G., Rowley. 



Plate 48. Figs. 16, 17, 18. 



Our specimen seems to have some affinity with the above species. It seems 

 to have six large and two small plates in the first row, the second row having 

 seven, the third has eight, the fourth eight, the fifth eight. The sixth row has 

 the same number, four of which bear elliptical scars for the attachment of 

 spines, perhaps, and a fifth has a rather large quadrangular hole at its lower 

 suture, from the standpoint of crinoids, an anal opening. The top row seems 



