PROCEEDINGS OF THE NATIONAL MUSEUM. G13 



The interlobes vary greatly in number aud position, as shown by Plate 

 XXXI, fig', la. The exumbrella surface is shown by Fig. 7/>. There does 

 not appear to be a true central oral opening; and a carefnl study of the 

 specimens leads to the view that the free inter and basal lobes or arms 

 served as the oral arms and conveyed food directly to the intestine or 

 stomach in the central axis. 



LAOTIRA, new genus. 



Discomedusiie with a lobate umbrella, 4, 5, 0, 7, to 12 or more lobes in 

 the simple forms, and with a larger number in the comi)lex forms; 

 without tentacles and without (?) central oral openings; with a simple 

 ladial canal in each lobe of the umbrella and in the iiiterradial lobes, 

 attached to the central axis, when they are present; oral arms rep- 

 1 esented by interradial lobes attached to the central axis and to the 

 subumbrella lobes; reproduction sexual or by fission. Type, Laotira 

 camhria. 



LAOTIRA CAMBRIA, new species. 

 (Plate XXXII, tigs. 1-8.) 



The range of variation in this s})ecies is much greater than that of 

 BroolscJla (dicrnata. Its general characteristics are shown by the fig- 

 ures illustrating it. In the simpler forms it has a radiating structure, 

 very much like that of i>. alternata (Plate XXXII, figs. 1, 2, and 3). A 

 departure from this is shown in the subumbrella surface of Fig. ?>a, and 

 still more in Figs. 4 and 4a. This is carried still farther in Fig. 5. The 

 tendency of the species to reproduce by fission is shown by Fig. 0. 



This si)ecies ])ossesses radiating canals in the exumbrella lobes in the 

 simple forms and irregular canals in the complex forms, as shown by 

 Plate XXXI, fig. 8. 



Xo central oral openings have been seen, but there is an unusual 

 development of the oral arms in the simple type; and in the complex 

 type, the variation of which is almost endless, the oral arms appear to 

 be numerous and attached irregularly to the subumbrella surface. This 

 is partly shown by Fig. 4</. 



This announcement is preliminary to a full illustration and descrij)- 

 tion, wdiich will appear as a monograph of the U. S. (leological Sur- 

 vey. A description will then be given of the mode of occurrence, 

 conditions of preservation, and other facts which may be of interest 

 in connection with this remarkable group of fossil Meduste. 



EXPLANATION OF PLATES. 

 Plate XXXI. 



BroolscUa alternata. 



Fig. 1. An exnniltrella with uiiie lolies, ami preserving a tr;»ce of the corona fnrrow 

 in the ring about the central disk. 

 la. View of the under or snbunihrella side of lig. 1. The narrow SMiuunlirclla 

 lolies are -well shown, and also wliat appears to l)e the oral arms, .r x. 

 A slight circuhir depression at the center {x') may indicate the position 

 of an oral aperture. 



