BRACHIOPODA. 213 



0. carinata, Hall. In the Lower Carboniferous are 0. SwaUowi, Hall, 0. resupiiiata, 

 Martin (?), and in the Coal Measures, 0. resupinoides, Cox. 



The term Hysterohthus 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 Linnk * and 

 ScHLOTHEiMf With more especial reference to the internal casts of Orthis striatula, 

 Schlotheim, a characteristic member of this group, and tlie name has been 

 resuscitated by some later writers, but nothing w^ould be gained by the adoption 

 of this term in place of ScHizornoRiA, especially as its early use was vague and 

 without generic sisinification. 



o^ 



ORTHOTICHIA 



(nom. propos). 



XIII. Group of Orthis ? Morqaniana, Derby. 



PLATE VU, FIGS. -11-15. 



From a personal examination of examples of tliis species, and from Dr. 

 Derby's detailed description and illustration, | it appears to be very closely 

 allied in all external and many internal characters to the resupinate shells 

 constituting the sub-genus Schizophoria. The es.sential 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 lamellge, 

 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 resupiiiata 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 Tes.'iinuitiuni, p. i*0, 1755. 

 1 Die Petiefactenkunde, p. 247, 1820. 



X Bulletin of the Cornell University, vol. 1, i^fo. 2, pp. 29-32, pi. iii, tigH. 1-7, 9, 11, 34 ; pi. iv, ligs. G, 14, 

 15. 1874. 



