402 



rather flat, most elevated along the median line, broadly rounded in front, 

 its sides nearly straight and sub-parallel, slightly converging from behind 

 forwards. On each side of the median line there are three or four obscure 

 depressions which represent the glabellar furrows. The length of the 

 glabella appears to be about once and a half its width at the neck segment. 

 Eyes, cheeks, thorax and pygidum unknown. Length of largest head 

 seen, twelve lines ; length of glabella, seven lines : width of glabella at 

 base five lines, at front margin four lines and a half. 



The head of this specis differs from D. magnificus in having a more 

 elongated and depressed glabella with the wide border in front smooth 

 instead of ornamented with radiating ridges. 



Limestone, No. 1. 



DlKELOCEPHALUS OWENI. (N. Sp.) 

 Fig. 379. 



Description. Head with a broad punctured and striated margin in 

 front of the glabella ; the latter oblong conical depressed, most elevated 

 along the median line, and with from two to four obscure depressions on 

 each side, representing the glabellar furrows. The front of the glabella is 

 broadly rounded, the sides straight or nearly so, sub-parallel or slightly 

 converging from behind forwards ; the posterior margin straight in the 

 middle, turned forward at the sides. At the base of the glabella there is 

 an obscure transverse furrow, and I am not sure whether this should be 

 regarded as the posterior glabellar groove or the neck furrow. The front 

 of the head is strengthened by a depressed convex rim just within which 

 there is a curved row of punctures, four or five in one line. From these 

 punctures fine somewhat flexuous striae converge towards the front of the 

 glabella. Eyes, cheeks, thorax and pygidium unknown. 



Length of head of a specimen which appears to be of the average size 

 ten lines ; length of glabella, seven lines ; width of glabella at neck seg- 

 ment five lines and a half, and at front margin four lines and a half; width 

 of the marginal rim, one line and a half. 



The depressions representing the glabellar furrows are sometimes obso- 

 lete, and sometimes only one or two are visible on each side. 



One of the specimens has the anterior striated margin proportionally 

 one fourth narrower than the above and only five punctures in the width 

 of one line. The glabella is smooth and not narrowed in front. I do not 

 at present think, however, that these differences are of specific importance. 



In another specimen where the crust is preserved, the punctures are 

 scarcely visible, but where it is removed they are distinct. 



Dedicated to Dr. D. D. OWEN, whose extensive geological researches 

 in the Western States have been of such great service to science. 



Limestone, No. 1. 



