304 



PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



The genus Kyammodes Jones, founded on a British Devonian spe- 

 cies, but thought to include also a few Silurian forms (as, for instance, 

 Kla dt nia kiesowi Krause), doubtless is closely allied to and probably 

 evolved out of typical Klosdenia. Though distinguished chiefly by 

 the much greater inequality of its valves, the thick ventral edge of 

 the right overlapping the smaller left valve, there are some peculiar 

 differences in lobation also. In all the species there is a deep median 

 furrow that, however, dies out before reaching the middle of the 

 valve. In Kyammodes kiesowi (Klcedenia kiesowi Krause) the parts 



52 



55 



QD CD 



r ■ 



X 



Vies. 52-60.— 52, 53. Right valve of Klcedenia wilckensiana (Jones), x 8 (female 

 individual), and p.eyrici1ia salteriaxa jones, x 10, respectively, showing the 

 relation' of khedenia to the b. salteriaxa group. (after jones and reutbr.) 

 54. Left side, end, and ventral views of complete carapace of Klcedenella Penn- 

 sylvania (Jones), X 15. (Copied from Jones.) 55, 56. Right and left valves 

 of Klgedenia neaki'assi (Weller), x 6. (After Weller.) 57,58. Left and right 

 valves, the latter a female form, of Kyammodes kiesowi (Krause), X 1". 

 (after Krause.) 59, 60. Left valve and anterior view of complete carapace of 

 Kyammodes WHIDBORNEl .Jones, X 20. (AFTER Jones.) 'I'm: SIMILARITY of Klce- 



DEX1A. KLCEDENELLAj KYA M MODES, AND THE BSYRICHIA SALTERIAXA GROUP ARE SHOWN 

 IX THE ABOVE FIGURES. 



of the valve are arranged almost regularly bilaterally with respect 

 to this furrow, which separates two subequal, low nodes, each taking 

 ii]) about one-fifth the total length of the valve. The outer limits of 

 tln'-,c nodes are defined by shallower converging furrows, which in 

 turn set oil' another matching pair of similarly curving low ridges. 

 \\\ K . whidbornei, the type of the genus, the lobes an 1 both less regular 

 and less constant in their development, the posterior median lobe, 

 which corresponds to the median lobe of hlodcnia. being especially 

 variable. As a rule it is smaller and set farther down than the antero- 



