BRACHIOPODA. 
101 
by. Tetractinella includes forms with four ribs on each valve. 
62. Pentactinella includes those with five ribs on each valve. 
63. Anomactinella includes those with a number of ribs sharply de¬ 
veloped toward the margin. 
2 . Amphitomella ; smooth shells with a very strong cardinal plate, and a 
median septum in each valve extending the entire length of the shell 
and dividing the cavity into two chambers. 
3. Dioristella ; smooth shells having a loop whose lateral branches return 
upon themselves, somewhat as in Meristella. 
Genus KAYSERIA, Davidson. 1882. 
PLATE XLI. 
1841. Orthis, Phillips. Palaeozoic Fossils Cornwall, Devon and West Somerset, p. Go, pi. xxvi, fig. 110. 
1842. d’Archiac and DE Verneuil. Descr. Older Deposits Rhenish Pi’ovinces ; Trans. Geol. 
Society, London, sec. ser., vol. vi, p. 396. 
1853. Orthis, Steininger. Geogn. Beschreibung der Eifel, p. 80, pi. v, fig. 5. 
1864. Atrypa, Davidson. British Devonian Brachiopoda, p. 51, pi. x, fig. 1. 
1871. Retzia, Qdenstbdt. Petrefactenkunde Deutschlands; Brachiopoden, pi. li, figs. 21-25. 
1871. Retzia, Kayser. Zeitsch. der deutsch. geolog. Gesellsch., vol. xxiii, p. 161. 
1882. Kayseria, Davidson. Devonian Brachiopoda, Supplement, p.'21, pi. ii, figs. 11, 12. 
Orthis lens, Phillips, the type-species of this genus, is a small middle Devonian 
shell, with depressed-convex or lenticular valves, radially plicated exterior, 
and a median plicated sinus on both valves. Its external expression is not unlike 
that of some of the retziiform species which belong to the genus Rhynchospira, 
though it possesses an impunctate shell. The complicated internal organiza¬ 
tion has been elaborated by the Rev. Norman Glass and described at length by 
Mr. Davidson. The pedicle-valve bears a low, thickened median ridge, but is 
otherwise devoid of pronounced peculiarities. In the brachial valve there is a 
high median septum which arises from beneath the divided hinge-plate and 
reaches its greatest elevation at a point behind the center of the valve, whence 
it descends rather abruptly, traversing altogether about two-thirds the length 
of the valve. 
The spiral cones form sharp angles with the crura, and are directed laterally ; 
the loop is very stout, taking its origin at about one-third the length of the 
