510 Systematic Paleoxtology 



away from the margin of the doublure, giving the caudal shield a semi- 

 circular outline. 



" Surface ornamentation. The surface of the cephalon, within the 

 border and occipital ring, is covered by strong tubercles, which are closely 

 disposed over the cheeks and more scattered on the glabella. In old in- 

 dividuals these tubercles extend to the margin, and the orbital ridge of 

 the cheek becomes covered with fine granulations. The surface of the 

 thorax and pygidium is smooth or finely granulose. Pygidia of young 

 individuals show low nodes or tubercles upon the pleurae, apparently ar- 

 ranged in three or four oblique rows with indications of similar orna- 

 mentation upon the axis." Hall and Clarke, 1888. 



From the Oriskany conies a nearly complete pygidium which bears a 

 close resemblance to Hall and Clarke's description and figures. This 

 pygidium has, however, a much stronger duplication of the pleural annula- 

 tions and the axial annulations are arched slightly medially. Neverthe- 

 less, the specimen must be placed here for the present, though it may 

 ultimately be shown to belong to another si>ecies. 



Occurrence. — Oeiskaiv^y Formatiox, Eidgely Member. Locality un- 

 known. 



Collection. — Maryland Geological Survey. 



[Ohern.] 



Subgenus HAUSMANNIA 



Dalmaxites (Hausmaxxia) pleuhoptyx (Green) 



Plate XCIII, Figs. 6-10 



Asaphus pleuroptyx Green, 1832, Mon. of Trilobites of North America, p. 55. 

 Dalmania pleuroptyx Hall, 1859, Nat. Hist. N. Y., Pal., vol. iii, p. 356, pi. 



Ixxiv, figs. 5 ?, 9 ? (not figs. 1-4, 6-8, 10-12) ; pi. ixxv, fig. 1 ?, 1861. 

 Dalmanites (Hausmannia) pleuroptyx Hall and Clarke, 1888, ibidem, vol. 



vii, p. 28, pi. xio, figs. 1-3. 

 Dalmanites pleuroptyx Weller, 1903, Pal. N. J., vol. iii, p. 295, pi. xxxii, fig. 1. 



Description. — " Head semicircular, with the posterior side concave, and 



the posterior angles prolonged to the fifth or sixth articulation of the 



thorax : frontal limb slightly concave, thickened at the margin. Glabella 



convex in front ; length from the annulation to the anterior of the frontal 



lobe, equal to the width of the frontal lobe, which is transversely oval: 



