388 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.56. 



Davidson says: "We certainly have the type hiforata and the 

 variety lynx, but these two seem with us so intimately connected that 

 I have combined them under Schlotheim's single designation; * * * " ^ 



Davidson figures ^ his specimens as PlatystropMa hiforata and varie- 

 ties of that species. The origin of the phcations of the fold and sinus 

 as showTi in figs. 11, Ua, 11& is distinctly different from that shown in 

 figures 12, 14, 15, 25. The origin of the phcations of the other speci- 

 mens is not determinable with certamty. This difference in origin 

 is of great importance as it takes place very early in the development. 

 Members of the same species would necessarily have a uniform 

 ontogeny. 



McCoy describes Platystroplda hiforata as "having the mesial fold 

 wider, and less elevated, bearing usually from six to nme ribs, at six 

 lines or less from the beak, and five to seven in the sinus; the lateral 

 ribs narrow, simple and from nine to twelve on each side, at six lines 

 from the beak."^ This description does not define any particular 

 form as there are individuals of nearly every species of the genus 

 which show this characteristic. 



As it is impossible to determine what Schlotheim's type-specimen 

 was it can not stand as a type of the genus. PlatystropMa laticosta 

 Meek is well known to all investigators of Ordovician paleontology. 

 As it possesses all the quahties necessary for a genotype, it is sug- 

 gested that future workers regard it as such. 



RELATION TO OTHER ORTHIDS. 



Professor Cumings has shown that the nepionic development of 

 Platysiropliia is identical with that of Orusia lenticularis variety 

 lycoicles Matthew and concludes that that species is the ancestor of 

 the genus. ^ 



EoortUs of the Upper Cambrian has the physiognomy of this genus 

 and has been confused with it. This resemblance is of little impor- 

 tance. It is, however, of interest that in this genus the sinus is in the 

 brachial valve and the fold on the pedicle valve. This recalls the 

 early development of PlatystropMa, in which the pedicle valve bore 

 a fold and the brachial valve a siaus. In Monograph 51, United 

 States Geological Survey (pi. 93, fig. 3), EoortMs'i diahlo (Walcott) 

 is represented. Tlie specimen seems to have been smooth at the 

 beak. Very near the beak broad undulations arise and extend to the 

 frontal margin. This agrees with the early nepionic development of 

 PlatystropMa and further investigation is hkely to bring to hght close 

 relationships between the two genera. 



The resemblance of PlectortMs to PlatystropMa has also been 

 demonstrated by Professor Cumings.^ He says: "If the sinus and 



1 British Fossil Brachiopoda, 1851-1855, p. 271. « Amer. Journ. Sci., ser. 4. vol. IS, 1903, p. 5. 

 ' Idem, pi. 38. ' Idem, p. 11. 



» British Pal. Fossils, pp. 192, 193, 



