70 



LINDSTRÖM, VISUAL ORGANS OF THE TRILOBITES. 



Schmidtia Marcou. 



Moberg has in his paper on »Sveriges äldsta Trilobiter», pl. 15, hg. 6, drawn a 

 hypostoma of Schmidtia Torelli with scars of maculse, placed like that of the Paradoxidae. 

 There is no mention made of them in the descriptions. 



Trochurus Beyrich. 

 Tr. pusillus Ang. 



' Pl. IV figs. 52, 53. 



The stränge transverse, bi partite hypostoma carries the small, round, tubereulose 

 maculae on the superior moiety. As seen from the interiör (fig. 53) they are obscurely 

 maculate, bnt it is doubtful whether Ihese black döts are derived from lenses, as the 

 snrrounding hypostomic snrface also has the same mottled aspect. 



Trochurus sp. 



Pl. IV figs. 54, 55. 



This hypostoma belongs to an nnknown species of Trochurus from the Southern 

 Gotland (Burs). Its maculae are placed almost as in the preceding species, but are much 

 larger. They are surrounded by prominent margins. No lenses have been discovered 

 on them. 



