[MATTHEW] STUDIES ON CAMBRIAN FAUNAS IGQ' 



This species will be seen to resemble P. Piochensis, Wale, from the 

 Upper Cambrian of Nevada.^ 



PTYCHOPARIA. 



Ptychoparia Adamsi. Billings sp. (PI. IV., tig. !).) 



Conocephalites Adamsi, Bill., Pala?oz. Foss., vol. i., p. 12, fig. 15. 

 Conoccphalifes vulcanus (.^), Bill., Palœoz. Foss.. vol. i., p. 14, fig. 17. 

 Ptychoparia Adamsi, Wale, U. S. Geol., Bull. 30, p. 195, pi. xxvi., figs. 1, 1 a 

 to c. 



Ptycho2xtria Adamsi, Wale, Olenellus Fauna, p. 649, pi. xcvi , figs. 1, 1 a to c. 

 For description of the species seep. 181. 



The species is represented in the collection by two specimens, casts in 

 sandy shale, one quite too imperfect to be used. The other shows a better 

 outline of the shield than Billings gives, as he had not developed the 

 posterior angle. The matrix is too coarse to show the fine details of the 

 surface. Only the middle piece of the head-shield is known ; this may be 

 somewhat widened by pressure. 



For some cause the measurements given by Billings are incorrect, and 

 do not agree with his figure. The example before me has the following 

 dimensions : Length of the head, 3J lines ; length of glabella, 2 lines ; 

 width of glabella, scarcely 2 lines ; width at the front, 1^ lines ; distance 

 of eye from the side of the glabella, nearly 2 lines. 



It is. perha})S. doubtful if the species figured by Waicott is the same 

 as that described by Billings, for it has a narrower fixed cheek. 



On examining the fossil described by Mr. Billings as Conocephalites 

 Vulcanus. it appears to the writer to be a specimen of P. Adamsi, which 

 has been distorted by a backward pressure in the shale. 



SOLENOPLEURA, Angelin. 



SOLENOPLEURA ARENOSA. Bill. Sp. (PI. IV., fig, 10.) 



Conocephalites arenosus. Bill., Geol. Vermont, vol. ii., p. 950, fig. 855. 

 Conocephalites arenosus. Bill., Fala^oz. Fossils, vol. i, p. 15, fig. 18. 

 Ptychoparia Adamsi (part), Waicott United States Geological Survey, Bull. :îO,. 

 p. 195. 



For description see p. 182, ante. 



This is one of the Primordial species most imperfectly shown by 

 Billings, but his figure does not exhibit all there is in the specimens, which 

 are casts or movilds in slate, of the middle piece of the head-shield. 



It appears to the writer that this species should be referred to the 

 genus Solenopleura. since it possesses deep furrows around the glabella, 



1 Compare the furrows with those of A. microphthalmus, Aug., Palaeontolo. 

 Scandinav., p. 25, tab. xviii.. fig. 4. 



