9 



but the opsaiag^ are unknown. Cjluma comparatively large com- 

 posed of thin plates and tapering as in Sleleocysfiles. Type B. 

 Wethcrbi/i. 



BELEMNOCYSTITES WETHERBYI, 1). sp. 



Plaie f. Fig. 4, dorstd side of a specimen iriili pari of llir i-Dhtmu 



attached: Fig. •'<, dorsal side of another specimen ivitli 



column and part of the plates J^roken off : Fig. 



6, ventral side of sanie, part of the plales 



onhj lieing ilistiiigiiish(dile. 



In 1881 Professor A. G. Wetherby, in an article entitled "De- 

 scriptions of New Fossils from the Lower Silurian and Suhcar- 

 boniferous Kocks of Kentucky," published in Jour. Cin. Soc. Nat. 

 Hist., vol. 4, p. 177, pi. V, figs. 2 and 2a, called attention to a 

 "new genus and species" of cystideans, without attempting to give 

 it a name or determine its affinities. Fig. 4 is a rej^roduction of 

 his figure 2, which is, evidently, the dorsal side of the specimen. 

 He said of it: "The column is round and tapers rapidly. The 

 peculiar character of this anomalous fossil is the presence of a 

 single arm, originating between two large plates which form the 

 apex of the body on the (ventral) side. Seven plates of the arm 

 are shown. Near it, upon the left side, as shown in the figure, is 

 a small tubercle, evidently formed by valvular plates now silici- 

 fied so as to obscure their arrangement." Our specimen, as shown 

 in figures 5 and 6, is just like his, except the lower part is broken 

 away, and we have attempted to give a better view of the ventral 

 Bide than is shown in his figure 2a. We have given him the 

 honor of the specific name. 



Body compressed, convex on each side, within the marginal rim 

 of plates, outline subovoid, truncated at the base for the attach- 

 ment of a large column, which is composed of thin jjlates and 

 tapers rapidly. 



There are nine j)lates in the marginal rim, not including (he 

 two which abut upon the column. Five on one side and four on 

 the other. These plates are large and sutures distiuct. The 

 sutures are exactly opposite each other on the two sides and are 

 plainly shown curving over the margin, which is thin and sharp. 

 This peculiar rim of plates increases in thickness ou the ventral 



