PALEONTOLOGIC CONTRIBUTIONS 



145 



Fig. 



a t r a 



D i o n i d e 

 Diagram- 



the exception of Jaekel 1 was that they were not connected with the 

 suture line (" nervures " of Oehlert). Exactly like lines occur in 

 Dionide, already well figured by Barrande (see text fig. 43), and 

 Ampyx hornei, as figured by Reed (see text fig. 44), all 

 often cited "blind" forms. In a specimen of Dionide 

 f o r m o s a where the lines reach the lateral furrows, we were 

 able to recognize also probable vestigial eyes in the furrows at the 

 end of the suture lines, appearing as 

 elliptic thickenings of the crust on the 

 inner side of the latter. A figure of 

 Dionide atra by Reed (see text 

 fig. 45), in which only one of the lines 

 is given, but is shown cutting the pos- 

 terior margin and there bounding the 

 limb or "brim," — to use Bather's better 

 term — is further evidence of the sutural 

 character of these lines. Corroborative 

 evidence of our inference that the cheek 

 lines of Cryptolithus are true suture lines 

 extending to the lateral eyes was seen in 

 observations of Richter (no. 10), accord- 

 ing to which the marginal suture in Harpes is not homologous 

 to the suture of the other trilobites, but a secondary acquisition to 

 allow of molting. 



After we had reached the conclusion, proceeding from the 

 presence of median eyes on the glabella and the " lateral eye w 

 character of the other eyes on the cheeks, that Cryptolithus is not 

 a true Hypoparian trilobite, and written out our notes, most 

 gratifying corroborative evidence reached us in the paper by Swin- 

 nerton (no. 11) who, on other evidence independently from 

 Richter and the present author, has reached the conclusion that 

 these genera are not Hypoparia, and has altogether dissolved this 

 order and redistributed the families among the Opisthoparia. 



Jaekel's view that the free cheeks have coalesced with the fixed 

 cheeks in the Hypoparia and the sutures disappeared, with the 



45 

 Salter. 



matic restoration of head 

 shield, showing facial su- 

 ture. (From Reed) 



1 Jaekel with his characteristic astuteness has years ago pointed out in 

 " Uber die Agnostiden (no. 6, p. 387) that the absence of eyes and sutures 

 go- hand in hand, and that the Trinucleidae, Ampycidae and Harpedidae 

 are not Hypoparia, but that since they show traces of eyes, there were 

 originally also sutures on the cheeks which have disappeared. 



