550 



Forty- fifth Report on the State Museum. 



opposite valve. The muscular scallops are represented by three 

 depressions, closer together than in the other valve. The plat- 

 form is here more highly developed and shows on its surface 

 indications of the median and lateral muscular scars. No median 

 septum is present in this valve. 



Type, Lingulojps Whitfieldi, Hall. 



Distribution. Silurian (Hudson River — Magara groups). 

 Four species are known in North and South American faunas. 



Lakhmina, (Ehlert. 1887. 



Synonym ; Davidsonella, Waagen. 



General outline more or less linguloid. The pedicle-valve is the 

 larger and possesses a prominent apex, which is provided, on its 

 lower surface, with a deep furrow for the pedicle. In the inte- 



Fig. 243. 



Lakhmina linguloides, after; Waagen. 

 Pedicle-valve, Fig. 244. 



Brachial valve. 



rior of the pedicle-valve, the cardinal margin is somewhat thick- 

 ened, without forming a distinct area. Below this is a not 

 very large triangular vaulted platform, supported by a median 

 partition not extending beyond its anterior margin. This plat- 

 form is inclosed by low, rounded ridges which originate near 

 the pedicle-furrow; its surface is flattened medially, but con- 

 cave on the sides. Of muscular impressions nothing has been 

 observed. In the dorsal valve the cardinal margin is but little 

 thickened and slightly curved. In the middle it bears a thickened 

 process, which is directed somewhat upward and inward, extend- 

 ing partly into the apical cavity of the other valve. From 

 beneath this process, a short thickened platform takes its origin ; 

 it is not even on the upper surface, but to all appearances spirally 



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