NO. 2144. NEW BRACHIOPODS FROM MAINE— WILLIAMS. 75 



regular fine lamellose lines fringed at their outer edges by fine inter- 

 rupted radial lines. Molds of the interior of some brachial valves 

 show a faint linear depression (elevated line in shell) in the umbonal 

 portion of the mold. 



From the above description it will be seen that the shell closely 

 resembles Davidson's narrower forms of S. elevata Dalman. 



Fm^mation. — Edmunds formation (Silurian). 



Locality. — Northeast corner of Crowe Neck, Trescott Township, 

 Washington County, Maine. 



Cotypes.—C^t No. 61451, U.S.N.M. 



Remarks. — It is Imown that specimens identified as Delthyns ele- 

 vata Dalman possess a median septum in the pedicle valve which has 

 led to the adoption of that species as the type of the genus Delthyris.^ 

 It is not established, however, either that Dalman recognized that 

 character in his descriptions or that the type-specimens possessed 

 this distinction. 



Lindstrom, in his description of the species from Gotland,- makes 

 no mention of the median septum. (The writer is indebted to Mr. 

 Hermanson, of Cornell University, for the translation of this descrip- 

 tion. ) The discovery in the Edmunds formation of Maine of the two 

 species here defined (which externally are very close to the form 

 called Belthijris elevata Dalman from Gotland and Spinfera elevata 

 Dalman of Davidson from the Wenlock of England, but differ from 

 each other by the possession of a well-defined median septum in one, 

 i. e. Sp. trescotti.^ and its absence in the other, i. e. Sp. cohscooki, 

 leaves us in doubt as to the validity of the generic characters of Del- 

 thyris Dalman. 



Davidson's conception of the species, as above quoted, appears to 

 be based upon external characters, and we note no mention of a 

 median septum in his description or figures. 



Wenjukow,^ in citing the species from the Silurian of Podolia, 

 seems to base the identification upon external characters alone. 



In all these definitions of the species Delthyris (or Spirifera) 

 elevata Dalman the groove along the middle of the fold of the 

 brachial valve is noted as one of the specific characters. 



In the various specimens here under investigation it is noted 

 that those forms in which the fold of the brachial valve is grooved 

 (viz, Spirifer cohscooki) have no median septum in the pedicle valve 

 and those forms possessing the median septum have no groove along 

 the middle of the brachial fold. While it does not necessarily fol- 

 low that the combination of characters expressed by species in Maine 

 should be the same as in species of the same approximate age in Got- 



1 Schuchert. Syn. Amer. Foss. Brach., Bull. U. S. Geol. Surv., No. 87, 1897, p. 200. 



2 Ofersigt. Kgl. Vet. Akad. Forhandlinger, 1860, p. 359-.360. 



^ Wenjukow, T., Die Fauna der Silurischen Ablagerungen des Gouvernments Podolien, 

 1899, p. 129. pi. 11, figs. 3, 4, and 5, 



