68 



PEOCEEDINGS OF THE ACADEMY OF 



that are somewhat wider than long, and provided with a very deep ambulacral 

 furrow within. Minute ambulacral pieces extending up the furrows of the 

 arms, from five to seven to each arm-piece, in each row, the two rows arching 

 over the deep furrow. Proboscidiform ventral tube very long, slender, cylin- 

 drical, and composed of apparently not more than two or three vertical 

 ranges of oblong curved pieces, about half as long as those of the arms. 



Column comparatively rather stout, rounded, and composed near the base 

 of more or less irregular pieces, gradually becoming thicker farther down, and 

 all pierced by a small rounded or subpentagonal central canal. 



Surface, when well preserved, showing under a strong magnifier minute 

 granulations, with a tendency to run together into a kind of vermicular style 

 of marking. 



Height of body of a medium sized specimen, to the top of the first radial 

 pieces, 0-16 inch ; breadth 0-28 inch ; height to top of second radial pieces, 

 0-30 inch. Length of arms, about 3 inches ; breadth of same at the base, C-15 

 inch. Thickness of column, 0-10 inch. 



This species will be at once distinguished from all the others known to us, by 

 having its body obtusely rounding under to the column below, instead of ex- 

 panding upward from the same, with straight or concave sides. By this char- 

 acter alone of its body, exclusive of the second radials, when found detached, 

 it can be readily distinguished from S. dentattis,Oyven and Shumard, as well as 

 from S. Wortheni and S. papilla tus, Hall. 



We have elsewhere noticed the occurrence of a long pipe-stem-like ventral 

 tube in this genus, and a double series of minute ambulacral pieces extending 

 up, and apparently arching over, the ambulacral furrow of each arm.* These 

 characters were first observed in this species, in which the ventral tube seems 

 to be nearly as long as the arms. We have also seen indications of the same 

 characters in 8. Wortheni, and fragments of other undetermined species, and 

 hence have little doubt that they occur in all the species of the genus, when 

 well preserved. There is perhaps scarcely any other type of all the various 

 geaei-a of Crinoids, in which one would less expect to find such an elongated 

 ventral tube, than in this. 



Locality and Positton. Upper division of the Burlington group, Burlington, 

 Iowa. Lower Carboniferous. No. 335, of Mr. Wachsmuth's collection. 



Synbathocrinus brevis, M. and W. 



Body small, expanding rather rapidly, with nearly straight sides from the 

 base to the top of the first radial pieces, thence contracting very slightly to 

 the top of the second radials. Form and arrangement of the body pieces very 

 nearly as in the last. Arms comparatively short, and tapering rather rapidly 

 at the extremities, angular or subcariuated along the middle of the dorsal side, 

 the carina being interrupted, or obsolete near the sutures between the arm- 

 pieces, so as to j)resent, as seen in outline, a subcrenate appearance ; arm- 

 pieces eighteen to each arm ; excepting the first one, slightly wider than long. 

 Column slender, round and composed of alternately thinner and thicker pieces 

 near the base ; some of those 0-25 in. farther down, however, being as long 

 as wide, all marked with strong radiating striae on their articulating surfaces, 

 and pierced by a small, apparently round, central canal. Surface finely 

 granular. 



Height of body to the top of the first radial pieces, 0-15 inch, to top of second 

 do., 0-20 inch ; breadth, 0-21 inch ; length of arms, 1-35 inches. 



This species will be readily distinguished from S. Wortheni^ S. denfatus and 

 /S. papillatus, by its much shorter arms, which have scarcely two-thirds as many 

 pieces as in those species. Its body is also rather less spreading, and slightly 



♦Sometimes these pieces are thrown apart along the middle, as if they had been mova- 

 able and articulated so as to open or close together over the ambulacral furrows. So 

 far as we have been able to see there would appear to be no pinnulse in this genus. 



[April, 



