BRACHIOPODA. 301 



of internal characters, the most striking of which are, the strong dental lamellae, 

 prolonged into the interior of the valve as vertical walls, forming the lateral 

 boundary of the muscular impression; the cardinal process, quadrifid on its 

 posterior and bifid on its anterior face ; the very large, broad, much elongated 

 spiral brachial ridges, which make something more than a single convolution. 



It is observed by Mr. Beecher that these spiral ridges are better comparable 

 to the so-called reniform impressions of the productids than to the brachial 

 supports and ridges in Koninckixa and Davidsonia. Elsewhere will be found 

 quoted the opinion of the late Professor Neumayr, that the reniform impres- 

 sions in Chonetes, Productus, etc., were produced by the coiled arms of the 

 animal. The presence of a cardinal process like that in Choxetes and Pro- 

 DUCTELLA seems to sustain the view of the closer relations of Lept^nisca to 

 this rather than any other group of the articulate brachiopoda. In regard to 

 the degree of attachment of the pedicle- valve, two additional species, from the 

 same formation, afford some interesting facts. Leptanisca concava has the cica- 

 trix restricted to a very narrow area about the umbo ; L. tangens, a smaller 

 species, is usually found adhering to branches and fronds of bryozoa, and the 

 scar is often deep and may cover the umbonal area ; while L. adnascens is 

 attached by the entire external surface of the pedicle-valve, generally to shells 

 of other brachiopods, preferably to Orthis. A young individual of the last 

 species retains the brachial valve, and shows a well defined cardinal area and a 

 prominent arched deltidium. 



Genus DAVIDSONIA, Bouchard 1849. 



PLATE XVa, figs. 31-33. 



1845. LepUBnaf, db Vbesboil. Geol. Rusaie et des Mont, de rOural, p. 227, pi. xv, fig. 9. 



1849. Davidsonia, Boochabd. Annals des Sciences Naturelles. 3d Ser., vol. xii, p. 92, pi. i, fig. 2. 



1852. Davidsonia, de KosiiXK. Mem. de la Societe Royale de Liege, vol. viii, p. 149, pi. i, figs. 1-4 ; 



pi. ii, fig. 1. 



1853. Davidsonia, Datid.so.v. Introd. British Fossil Brachiopoda, p. 110, \<\. \\\\, figs. 186-193. 

 1853. Davidsimia, Schxdr. Palseontographica, vol. iii, p. 219. pi. xxxix, fig. 4. 



1855. Davidsonia, de Koxi.vck. Mem. de la Societe Royale de Liege, vol. x, p. 281. 



1858. Davidsonia, Davidsos. The Geologist, No. xi, pi. xii, tigs. 33, 34. 



1865. Davidsonia, David.so>-. Bi-itish Devonian Bi-achiopoda, p. 74, pi. xi, tigs. 13-16 ; pi. xv, fig. 18. 



1871. Davidsonia, Qcesstedt. Peti-efactenk. Deutschl.-inds, Brachiopoden, p. 6S9, pi. Ixi. figs. 103-109. 



1S71. Davidsonia, Kayskr. Zeitschr. iler deulsch. geolog. Ge.selLsch., vol. xxiii, p. 632, pi. xii, fig. 9. 



