324 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



B. simplex and B. granulata " depart somewhat from the other 

 species in the more subdued development of both the anterior and 

 the median lobes. These two species strongly resemble Klwdenia. 

 Indeed, it is difficult to point out satisfactory differences. However, 

 as that genus became almost extinct with the close of the Silurian, 

 it seems highly unlikely that these Carboniferous species were directly 

 connected with it. 



Genus JONESINA, new. 



Reyrichia (part) Jones and Kirkby. Ann. and Mag. Nat. Hist. (5), XVIII, 



1886, p. 258; Geol. Mag., Dec. 3, III, 1SS6, p. 438. 

 Beyrichiella (part) Ulrich and Bassler, Proc. U. S. Nat. Mns., XXX, 



1906, pp. 151-155. 



Carapace small, about 1 mm. in length, usually elongate, the out- 

 line varying from subelliptical to oblong or approximating a par- 

 allelogram; greatest thickness in anterior half. Valves strongly 

 convex, variously lobed, unequal, the left being the larger, sometimes 

 overlapping the edge of the right on all sides. The most simple 

 types (J. craterigera and J . arcuata) are marked with a rather deep 

 dorsal sulcus situated somewhat behind the middle. The whole 

 area in front of this sulcus may be almost uniformly convex, or a 

 node may be obscurely defined in its post-dorsal quarter (that is, 

 just in front of the sulcus). Behind the sulcus a more clearly denned 

 node is always observable. In more complex species (-/. fastigiata) 

 three nodes are distinguishable, two, subequal, situated on opposite 

 sides of the main sulcus, and a larger, less definitely outlined, lobe 

 occupying- the anterior third. Finally, in ./. fodicata, the anterior 

 lobe is divided by the separation of a node simulating the other two 

 in size and form, while all three nodes will appear as connecting 

 below with a low marginal ridge. A more or less obscure and 

 variable ridge commonly unites the two median nodes, occasionally 

 producing an effect simulating Bollia. 



Genotype. — Jonesina fastigiata (Beyrichia fastigiata Jones and 

 Kirkby). 



The following additional species are referred to Jonesina: J. ar- 

 cuata (Bean) (as figured by Jones and Kirkby under the genus Bey- 

 richia)] 3 J. oradyana {Beyrichia Jones and Kirkby ), c J. craterigera 

 (Beyrichia Brady Ms., Jones and Kirkby) , d J. fodicata (Beyrichia 



"Jones and Kirkby describe tbe latter as a variety of /{. fortis. It seems to 

 the writers as allied to R. simplex rather than R. fortis, tbe post-median node 

 as well as the general expression of tbe valves, aside from tbe surficial crests, 

 being tbe same as in tbe former and quite different from tbe latter. 



& Geol. Mag., Dec. 3, III, 1886, p. 438, pi. xn, figs. 12-14. 



'■ Idem., tig. 11. 



d Idem., tigs, la, 7&. 



