31g PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



often produces an appearance suggesting the " loop " of a Bollia. 

 Surface generally smooth and polished, and without ornamental 

 markings. 



Genotype. — KIwdenella pennsylvanica ( Klosdenia pennsylvaniea 

 Jones). 



Of unquestioned species of this genus, some eight or ten, two of 

 them perhaps being merel}' varieties, are contained in the collections 

 of the U. S. National Museum. These range in time from the Clin- 

 ton to middle Devonian. A British Carboniferous species, published 

 by Jones and Kirkby under the name Beyrichia? hicaesa, probably 

 belongs to this genus. Except this and the two Devonian species, all 

 the others are confined to the Silurian rocks of the Appalachian 

 province. As a rule, the species are exceedingly prolific in the way 

 of individuals, the layers of limestone in which they occur being 

 almost literally made up of their remains. In most eases they occur 

 as entire shells, which, being easily freed from the matrix, are admir- 

 ably suited for detailed study. 



Only about half of the known forms have been described, and one 

 of these (described as Beyrichia trisulcata by Hall) has never been 

 adequately figured. Klwdenia pennsylvaniea, as figured by Jones in 

 1889 °, includes two distinct species and a variety, which are repre- 

 sented by thousands of specimens in the material available to the 

 writers. The form represented by Jones's figures 5a, b. c, d, and 6 is 

 accepted as the Klcedenella pennsylvanica. His figures 8 and 9 are 

 regarded as based on examples of our K. turgida, new species.' 1 while 

 7a and 75 probably represent a variety of the latter, here distin- 

 guished by the subordinate name ventrosa. 



°Amer. Geol., IV, p. 341, figs. 5-9. 



h Kloedenella turgida is distinguished from A", pennsylvanica, as here restricted, 

 by the strong development of the anterior sulcus. This sulcus delimits a well- 

 marked anterior lobe and produces a somewhat concentric arrangement of the 

 Lobes behind it. the effect being quite different from the usual appearance of 

 A . pennsylvanica. 



Length of a normal righl valve, 1.1" mm.; height, <>.c»4 mm.: length of a 

 short left valve. ().!>7 mm.; height, 0.60 mm. See Plate XLIII, figs. (!, 7. 



Formation and locality. — Coeymans limestone, Cumberland, .Maryland. 



Cotypes.— Cat. No. r>:!27s, U.S.N.M. 



"This form is more like K. pennsylvanica than K. turgida in lobation of tin 1 

 valves, being without a well-marked anterior sulcus, but in the less elongate 

 form and general aspect it is so like K. turgida that it has been placed as a 

 variety of this species. Its main peculiarity lies in a ventral swelling which 

 causes an apparent break in (he antero-niediaii lobe. The ventral flange is 

 unusually well developed and the series of granules along the antero-ventral 

 edge has nol been observed in any other species of the genus. See Plate XLIII, 

 fig. 8. 



Formation and locality. Coeymans limestone, Cumberland, Maryland. 



Holotype. ('at. No. ">:^7!>, U.SJST.M. 



