21S jS'civ Sjii'cies of Fossils from (Jhin. 



tion, giving u sigmuidal outline ; of the shorter sides, one is 

 straight to near the apex, where it becomes rounded, and the 

 other is slightly concave. Another form has the shorter sides 

 diverging at an angle of about 105 degrees, one slightly convex 

 and the other concave ; while the basal margin is convex in two 

 sections, with- a constriction or interruption between the two 

 sections, or at about one-third of its length from the straight 

 margin. The plates of this and the preceding form have the 

 surface regularly annulated transversely, parallel to the basal 

 margin, the annulations very fine, and regulai'ly increasing in 

 size and strength from the apex to the base, except in aged speci- 

 mens, where they are again crowded near the border : live undu- 

 lations may be counted in an eighth of an inch, where strongest. 

 These forms, also, have the straight margin often fractured and 

 bent, as if they had been broken along that side ; indicating that 

 two such plates may have been united along this line ; and on 

 the only individual showing sevei'al plates together, this wonkl 

 appear to be the case. A third form of plate is narrowly trian- 

 gular or conical, the basal border being the shortest, and sini[)ly 

 convex ; the other sides being sliglitly cuiwed throughout, l^nt 

 more distinctly so near the apex, which is obtusely rounded ; the 

 lateral margins are of unequal length, and the annulations of 

 the surface liner and more closely arranged than on the other 

 forms. 



The individual specimens are much too few in number to give 

 any very satisfactory idea of the general form of the complete 

 body, or of the number of ranges of i^lates of which it may have 

 been composed. Tliere appears to be no reason, however, to 

 doubt the correctness of the reference of these plates to the genus 

 PlumuUtes, Barrande, as their genera! form and surface struc- 

 ture is exactly like those given by Dr. Barrande, and also to 

 those given in Vol. II, Pal. Ohio, PL 4, Figs. 1 and 2 {P. Ja- 

 mesi), as occurring in the rocks of the Hudson Eiver group, at; 

 Cincinnati ; while some idea may be obtained of the probable 

 form of the entire body from the outline figure of a European 

 sjoecies, represented in Fig. 3 of the same plate. These Devonian 

 specimens, however, have been of very much greater size than 

 the above, as the plates here figured are all represented of natural 



