BRACHIOPODA. 
249 
the genus equivalent to Orthothetes, of Fischer de Waldheim, 1837, as now 
defined. 
In his “Monograph of the Permian Fossils of England” (1850, p. 103), 
Professor King, under the head of “ Family Strophomenidjb, King, 1846,” writes 
as follows: 
“Rafinesque was the first to found a genus for shells belonging to this family. 
Whether his Strophomena were ever published by himself, or it first appeared 
under the editorship of some other author, I have not been able to ascertain; 
but this is certain, that the genus was described by M. de Blainville, in his 
‘ Manuel de Malacologie,’ 1825, and afterwards in the ‘ Dictionnaire des 
Sciences Naturelles,’ t. li, 1827, in both of which it is typified by the American 
Strophomena rugosa, Raf., which, from its general form, and its large valve 
being concave, and the opposite one convex, I have little doubt is identical 
with the recently proposed Strophomena ( Leptrna) planumbona, of Hall.*” 
But King also included in the genus “ such shells as S. alternata, Conrad, 
S. Dutertrii, Murchison, S. euglypha, Dalman, S. planoconvexa, Hall, and several 
others”; a group in which are now recognized three distinct generic types 
of adult characters In 1853,f Mr. Davidson followed Professor King in 
assuming as the type “ S. rugosa , Raf. ? = S. planumbona or S. alternata ” 
This conception of the value of the genus Mr. Davidson did not modify 
in any of his subsequent writings, except in his last reference to it, in 
the “ General Summary ” of 1884. The reversal of the relative convexity 
of the valves in the above species, which was indicated in Defrance’s 
description of S. rugosa , and which is now regarded as an important mor¬ 
phological character, was not regarded by Mr. Davidson as of high value. The 
fact that the reversed species have, in early growth-stages, the normal convexity 
which is retained throughout by such forms as S. alternata , was considered as 
evidence of homogenity; hence he included in this genus “ all species agreeing 
with S. planumbona, alternata, grandis, filosa, euglypha, funiculata, antiquata, pecten, 
expansa, depressa, etc.,” although in this list are species with normal convexity 
* “ Vide Palaeontology of New York, vol. i, p. 112, pi. xxxi b, fig. 4 ; and Bull, de la Soc. Geol. de France, 
2me serie, t. v, pi. iv, figs. 3 a, b, c, d.” 
t Introduction British Fossil Brachiopoda, p. 105. 
