BRACHIOPODA. 
213 
O. carinata, Hall. In the Lower Carboniferous are 0. Swallowi, Hall, 0. resupinata, 
Martin (?), and in the Coal Measures, 0. resupinoides, Cox. 
The term Hysterolithus was applied by some early non-binomial writers to 
internal casts of these shells together with others, mostly spiriferoids, having 
the same general aspect. The term Hysterolites was used by Linne * and 
Schlotheim-J- with more especial reference to the internal casts of Orthis striatula, 
Schlotheim, a characteristic member of this group, and the name has been 
resuscitated by some later writers, but nothing would be gained by the adoption 
of this term in place of Schizophoria, especially as its early use was vague and 
without generic signification. 
ORTHOTICHIA 
(nom. propos). 
XIII. Group of Orthis ? Morganiana, Derby. 
PLATE VII, FIGS. 11-15. 
From a personal examination of examples of this species, and from Dr. 
Derby’s detailed description and illustration, :j: it appears to be very closely 
allied in all external and many internal characters to the resupinate shells 
constituting the sub-genus Schizophoria. The essential point of divergence is 
in the presence of a thin, elevated median septum longitudinally dividing the 
muscular area of the pedicle-valve, this, with the prominent dental lamellas, 
making three vertical plates in this valve. The character thus given to the 
interior, as shown in figures 6, 7, 9, 11, plate iii, of Dr. Derby’s work, is 
altogether distinct from that in Orthis resupinata and its allies, for while in 
these shells there is often a more or less prominent thickened median muscular 
fulcrum, it does not become a septum; futhermore, the muscular area, which 
in Schizophoria is deeply impressed and bordered by a thickened margin is not 
so in Orthis ? Morganiana, but appears to be on the same level with the general 
interior surface and faintly defined at its anterior edge. In the brachial valve 
the species has the multipartite cardinal process and the arrangement of mus- 
* Museum Tessinianum, p. 90, 1755. 
f Die Petrefactenkunde, p. 247, 1820. 
J Bulletin of the Cornell University, vol. 1, No. 2, pp. 29-32, pi. iii, tigs. 1-7, 9, 11, 34; pi. iv, figs. 6, 14, 
15. 1874. 
