DESCRIPTION OF GENERA AND SPECIES. 117 



conical, marked by two or more pairs of short furrows; occipital furrow clearly de- 

 fined ; occipital ring rounded. Fixed cheeks rather broad and convex. Free cheeks 

 subtriangular in outline, rising from the border to the eye-lobe with a gentle con- 

 vexity; a spine is attached to the lateral border a short distance in advance of where 

 the border is cut by the facial suture. Facial suture, cutting the anterior border 

 nearly on a line with the front base of the eye-lobe, extends obliquely across the 

 border, and then with slight curvature to the palpebral lobe ; curving about the latter, 

 it extends obliquely outward and backward, cutting the border at the postero- 

 lateral angle of the cephalon, and back of the spine extending from the border. 

 Eyes small, elevated, and situated about midway of the distance between the front 

 and posterior margins of the cephalon. 



The associated hypostoma of B. sinensis has a subrhomboidal outline; convex, 

 oval body with a transverse, curved furrow; the narrow, rounded border incloses a 

 small wing-like projection opposite the central body. 



Number of thoracic segments unknown. Segments associated with B. sinensis 

 have a strong central axis less than one-half the width of the pleural lobes ; pleural 

 lobes flattened about two-thirds the distance from the axis to the end of the segment ; 

 a flat groove begins near the axis and extends with a nearly uniform width to the 

 genal angle, where it narrows to the base of the spinose or falcate termination of 

 the segment. 



The pygidium associated with B. sinensis has a subsemicircular outline; axis 

 convex, strong, and divided into four or more transverse rings by transverse furrows; 

 lateral lobes depressed and divided by strong furrows into four or more segments 

 that cross the border and continue as spines of varying strength and length ; border 

 rounded and somewhat obscured by merging into the segments and the spines on its 

 outer margin. 



Surface granular in the type species. 



This genus differs from Damesclla Walcott, to which it appears to be most 

 nearly related, in having a flat, straight groove on the pleural lobe of the segments of 

 the thorax, proportionately broader furrows on the pleural lobe of the pygidium, and 

 a concave frontal limb on the cephalon with a narrow rim. Blackwelderia differs 

 from Teimstion Monke mainly in the character of the associated free cheeks and 

 pygidia and the frontal limb of the cephalon. It differs from Dorypyge Dames in 

 the form of the glabella and free cheeks. The straight groove of the pleural lobe of 

 the thoracic segments is much alike in the two genera and the pygidia are of the 

 same type. The thoracic segments of Blackwelderia are of the same type as those of 

 Olenellns Meek, but the cephalon differs in the glabella. From Stcphanocare Monke 

 it differs in the character of the frontal border of the cephalon and the pleural lobes 

 of the pygidium, as well as the pleural lobes of the thoracic segments. 



Genotype. Calymmene f sinensis Bergeron; second species, B. cilix (Walcott); 

 third species, B. alastor ( Walcott). 



Blackwelderia alastor (Walcott). 



Plate 9, Figures 7, -jn. 



Darypygella alastor WALCOTT, 1905, Proe. U. S. Nat. Mus., vol. xxix, p. 31. (Described and dis- 

 cussed as a new species essentially as below.) 



This species is represented by a single specimen of the central portions of a 

 moderately convex cephalon and several associated pygidia that occur at the same 

 horizon as Teinistion alcon [p. no]. Cephalon, as indicated by the specimen, trans- 

 versely semicircular and moderately convex. Glabella broadly truncato-conical, 

 narrowing to the gently rounded front; two pairs of narrow, short furrows extend 



