268 THE DEVONIAN OF MISSOURI. 



forming a faint border. Posterior margin of pygidium terminating bluntly, and showing 

 the beginning of two rudimentary spines. 



Cephalon and thorax unknown. 



Remarks — This species is represented by a single complete pygidium. It may be 

 differentiated from all other associated Dalmanites by the character of the posterior 

 margin of the pygidium. In this feature it seems to be a forerunner of such species 

 as Dalmanites (Odontocephalus) aegeria Hall, Dalmanites (Odontocephalus) coronatus 

 Hall, or Dalmanites (Odontccephalus) selenurus Hall, of the New York and Ohio Onon- 

 dagan fauna, which have the two posterior spines developed in a conspicuous manner. 



Horizon — Lower beds. 



Holotype No. 27536, Walker Museum. 



Genus Cryphaeus Green 



Cryphaeus sp. 



Plate 71, figure 21 



Description — Pygidium small, sub-oval, wider than long; the dimensions are: Length 

 9 mm., width 11 mm. The axial region is characterized by 7 well defined annulations, 

 broad and rounded, each one bearing in the middle a faintly defined node; intervening 

 grooves narrow and shallow. Pleural lobes moderately broad, sloping gradually toward 

 the lateral margin to near the edge where they turn and bend dorsally; each lobe bears 5 

 annulations which terminate in spines, the character of which cannot be determined 

 from the specimen. Each pleural segment is marked at the abrupt turn by a circular 

 depression which probably represents the base of a short node. Two additional ones are 

 present at the posterior of the pygidium, and from the base of each extends a short spine. 



Remarks — A single incomplete pygidium in the collection apparently represents an 

 undescribed species of this genus. In general shape, character of pleura and spines, it 

 resembles Dalmanites (Cryphaeus) comis, but differs in the larger size, in having an 

 additional axial annulation, and in the presence of nodes at the ends of the pleural seg- 

 ments. 



Horizon — Upper beds. 



Figured specimen No. 27547, Walker Museum. 



Genus Phacops Emmrich 



Phacops cristata Hall 



Plate 71, figures 23-25 



1888. Phacops cristata Hall and Clarke, Nat. Hist. N. Y. Pal., vol. 7, p. 14, pi. 6, figs. 



1-31, 16-29; pi. 8a, figs. 1-4. 

 1913. Phacops cristata Kindle, Geol. Surv., Md. Mid. Dev., p. 331, pi. 43, figs. 13-15. 

 Description — Cephalon of medium size, semi-circular in outline, genal angles 

 rounded. The dimensions of a nearly perfect head are: Length 16 mm., width 26 mm. 

 Glabella large, width greater than length, moderately convex, narrow posteriorly, and 

 rapidly expanding anteriorly, giving a subpentagonal outline. Anterior margin promi- 

 nent and projecting beyond the frontal margin. Laterally the glabella is separated from 

 the cheeks by deep, narrow furrows. The surface is marked by three pairs of glabellar 

 furrows, the anterior and middle two scarcely perceptible, the posterior pair strongly 

 marked, extending about half way across the glabella, and almost cutting off a narrow 

 segment at the base of the head. Cheeks small, confined to the posterior portion of the 

 cephalon, and bounded by a convex margin. Occipital furrow distinct, extending to, 

 and merging in the marginal border. 



