118 



actei-s hold througliout the life history of an individual. I'msser was the 

 first to refer this shell to T)crJii)uA\ 



On referring to de Kouiuck's figure of his Orthis i(inhracuhnn Schlot- 

 heim|j|| the striking sinularity will at once be apparent and by comparing 

 this figure and description with that of P.ronn.§§ of the FAftel Devonian 

 (apparejitly after examining the types), the difference between the typical 

 0. Hiiihraciiliiin and de Kouiuck's specimen, and the similarity of the latter 

 with the American species at once becomes apparent. Kouiuck's description 

 gives his species 108-109 striae and if this is true, it is hardly identical 

 with the American species as this (and de Kouiuck's figure) give IGO to 

 2C0 on a specimen of the same size. As to the question of the name of the 

 American species, it is distinct from O. loiihractiluni and Meek"s term will 

 take i)recedence for the American form. If they are identical, as seems 

 probable, it will also apply to de Kouiuck's shell. 



On comparison of typical specimens of this shell with the description 

 and figures of Hall and Clarke's Derhyn ciniihiiJu it will be seen that they 

 are all identical. This duplication is due to a habit of Mr. Meek's of 

 describing a species under one term, then at the close of the description 

 statin.g that in all probability it does not belong to the species referred to 

 but is probably a new species, then proposing the name at the end of the 

 whole descriptioi*.* 



(hie of the speL-imens obtained was fortunately C(jvered with young 

 specimeus of whose relation there can be no doubt as Deihtja mnltistiiata 

 is the only Derbya in this horizon at Torrence where these si)ecimens were 

 found. Thj smallest specimen measured a trifle over 1 mm. wide. In a 

 specimen 5 mm. wade the mesial septum is well developed. 



The high cardinal area is well illustrated by the measurements of a 

 small specimen. The pedicle valve length was lUmm. and width :! mm. 

 The cardinal area was nearly square' and measured 3 mm. x 2 mm., or 1-irger 

 than the pedicle A'alve. At no time in its development was it seen to have 

 a form identical with the tyjiical adult D. cruftfut. 



■ ttKansas- River Section of the Permian and Pernio-Carboniferous Rocks of Kansas. 

 Bull. Geo). Soc. Amer.. VI. p. 10. 1894. 



['iDescriptiou des Animaiix Fossiles de Koninck. pp. 222-221 and PI. XlII. fig:. 4a. b. c 

 et fig. 7. a, b. c. et PI. XIII bis. fier. 7, a. b. 



iiLethaea Geoguostica Bronn, pp. 368-363 and PI, ir, fig. 11. a 1), c. 

 *Pal. N. Y.. Vol. VIII. Ft. I, page 348 PI. lib. fig. 2-3. 



