VI * 



THE , CEPHALIC SUTURE LINES OF CRYPTOLITHUS 

 (TRINUCLEUS AUCT.) 



In the preceding paper on the median eyes of the trilobites it has 

 been stated that, the lateral eyes in Cryptolithns and Harpes appear 

 to have wandered away from the " suture " onto the apexes of the 

 fixed cheeks, thus having attained a position that together with 

 their primitive character, has invited their reference to the median 

 ocelli. This inference presupposes the assumption that the suture 



Fig. 43 D i o n i d e f o r m o s a Barrande. Cephalon showing median 

 eye tubercle and facial suture. (From Barrande) 



Fig. 44 Ampyx hornei Reed. Cephalon showing median eye tubercle 

 and facial suture. (From Reed) 



is marginal or hypoparious, as claimed by Barrande, Beecher and 

 many others. When the present writer became convinced that the 

 tubercle upon the glabella represents the median or parietal eye, 

 and that therefore the vestigial eyes on the cheeks must be true 

 lateral eyes, he began to look for evidence of this inference. The 

 most important evidence was seen, as stated in the preceeding 

 paper, in the eye line extending in the early growth-stages of 

 Cryptolithus to the eyes upon the cheeks. Further evidence was 

 found in two distinct suture lines (see pi. 35, fig. 6) extending 

 from the genal angles to the rudimentary eyes, and seen especially 

 well in the shale specimens from the Lorraine beds. On searching 

 the literature it was found that these lines had been noticed and 

 partly figured before, by Salter, McCoy, Barrande (no. 1), Oehlert 

 (no. 7) and Reed (no. 9), but the final consensus of authors with 



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