Report of the State Geologist. 1)9* 



locality of Anthony's fossils, and gave figures of two pygidia which, 

 for us, seem to establish the validity of Anthony's designation. At 

 the same time Meek gave figures of two glabellas {loc. cit., figs. 6, 7) 

 without proposing therefor any specific name. Both are character- 

 ized by long single occipital spine, that of figure 6 very broad and 

 stout, that of figure 7 much more slender. It appears that a cephalon 

 having the structure of the former of these was subsequently 

 described by S. A. Miller as Acidaspis anchoralis"^ and with this 

 cephalon Mr. Miller associated a pygidium having the same structure 

 as that of Geratocephala ceralapta as given by Anthony and Meek. From 

 Miller's description it does not appear how forcible the reason may 

 have been for including these separate parts under the same specific 

 name, but should subsequent investigations prove that these parts 

 referred to Acidaspis anchoralis do belong to the same species it would 

 seem that Mr. Miller's name must take its place as synonymous for 

 G. ceralepta, for Anthony's figures, though not all that could be 

 desired, show a very characteristic feature in the single pair of long" 

 pygidial spines, which do not occur in any other of the known species 

 of this fauna. 



In 1842 Dr. John Locke describedf the species Geraurus cro$sotus 

 from the same horizon at Cincinnati. Mr. Meek in the work cited 

 (p. 165, pi. 14, figs. 10 a, b) made an identification of doubtful 

 value (so regarded by him) of this form as a species of Acidaspis. It 

 is questionable whether this should be accepted as the species 

 intended by Locke and we prefer to refer to it provisionally as Gerato- 

 cephala crosota, Meek. 



In 1847 Professor Hall describedj Acidaspis Trentonensis and A. 

 spiniger. The latter has proved to be a Bathyurus. 



In 1885 Shumard described § Acidaspis Halli, from the Trenton 

 horizon of Missouri. 



In 1857 Billings described || Acidaspis Horaniirom. the Trenton lime- 

 stone, Riviere a la Friponne, near Cape Tourment. The original speci- 

 men is described as broken at the occipital ring so that its position 

 in this classification is uncertain. 



In 1873 Mr. Meek described^ in addition to the species already 

 mentioned, Acidaspis Gincinnatiensis, from the Hudson Biver group, 

 the original being a pygidium with two thoracic segments attached. 



♦Cincinnati Quarterly Journal of Science, vol. 2, p. 349, figs. 2-4, 1875. 



t American Journal of Science, 1st Ser., vol. u, p. 347, fig. 



t Palaeontology of New York, vol. I, p. 240, pi. 64, fig. 4, a-f; p. 241, pi. 64, fig. 5. 



§ First and Second Report Geological Survey of Missouri, pt. 2, p. 200, pi. B, figs. 7, a-c. 



II Report to Sir W. E. Logan for 1856, p. 341. 



IT PalsBontology of Ohio, vol I, p. 167, pi. 14. fig. 3. 



