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 Koninckina 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 Chonetes and Pro- 
ductella seems to sustain the view of the closer relations of Lept^enisca 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. Lept&nisca 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. Leptwria?, de Verneuil. Geol. Russie et des Mont, de l’Oural, p. 227, pi. xv, fig. 9. 
1849. Davidsonia, Bouchard. Annals des Sciences Naturelles, 3d Ser., vol. xii, p. 92, pi. i, fig. 2. 
1852. Davidsonia, de Koninck. Mem. de la Societe Royale de Liege, vol. viii, p. 149, pi. i, figs. 1-4 ; 
pi. ii, fig. 1. 
1853. Davidsonia, Davidson. Introd. British Fossil Brachiopoda, p. 110, pi. viii, figs. 186-193. 
1853. Davidsonia, Schnur. Palseontographica, vol. iii, p. 219. pi. xxxix, fig. 4. 
1855. Davidsonia, de Koninck. Mem. de la Societe Royale de Li&ge, vol. x, p. 281. 
1858. Davidsonia, Davidson. The Geologist, No. xi, pi. xii, figs. 33, 34. 
1865. Davidsonia, Davidson. British Devonian Brachiopoda, p. 74, pi. xi, figs. 13-16; pi. xv, fig. 18. 
1871. Davidsonia, Quenstedt. Petrefactenk. Deutschlands, Brachiopoden, p. 689, pi. lxi, figs. 103-109. 
1871. Davidsonia, Kayser. Zeitsclir. der deutsch. geolog. Gesellsch., vol. xxiii, p. 632, pi. xii, fig. 9. 
