52 



LINDSTRÖM, VISUAL ORGANS OF TIIK TRILOBITES. 



Cybele Loven. 



Cyb. bellatula Dalman. 

 Pl. IV tig. 2. 



Wc give ;i new figure of the hypostoma to complete that of Fr. Sciimidt, pl. XIII 

 tig. 9. The anterior wings are larger and obtuse, excavated below and the börder rim is 

 not so distinct all round as lic has figured. There are two pair of oblique, lengthened 

 groovcs above each other. The opposite do not, however, join to form a, coherent groove 

 across the median tield of the hypostoma, which is level between thcm. No maculee. 

 Nearer the anterior börder close below the wings, there is ;i small roundish, dark spöt. 

 The surface of the hypostoma is granulated. 



Cyphaspis A no. 

 Cyph. elegantula Ang. 



Pl. III figs. 22—25. 



The hypostoma is elongated, ;intcrior margin evenly arched, anterior wings tri- 

 angulär, lateral margins faintly curved as well as the posterior margin, at both sides of 

 which there is one diminutive spine. The posterior wings are short forming a spiny 

 process from the lateral margin. The surface of the hvpostoma is smooth with a shallow 

 transvcrse groove on the inferior moiety and two corresponding lateral impressions below 

 it, one on each side. The elevated lateral borders are longitudinally striated by ;i few 

 terrace lines. There are no maculae visible. The eyes consist of short hexagonal prisms 

 (figs. 22, 23) nearly resembling those of Proetus. 



Dalmanites Emmrich. 



In this large genus the hypostoma has been figured in ;i great number of species. 

 But it is only in the following that wc. ;it least in the figures, ii' not in the descriptions, 

 are able to detect the maculse. 



i), atavux Barr. Suppl. pl. 5 fig. 14. 



D. Calypso J. Hall, vol. VII, pl. XI A. tig. 21 p. 66 »Postero-lateral pits, moderately 

 strong and elongate». There are ensts of the two well distinct maculae. 



I). caudatus Brunn. 



a. Forbes ;hk1 Salter in British Organic remains, Dec. II pl. 1. fig. 3 givc a good 

 figure, showing the oblique pitlike maculaa. On page 2 is told that »a pair of lateral 

 strong indentations indicatea second furrow above» (»the transverse furrow between the tip»). 



1). Salter, pl. 3, figs. 7, s, bad figures, the description re.rbally the same ;is above. 

 \Vh;ii Angelin pl. \ III, fig. 2 c gives as the hypostoma of »Ph. caudata» is in fact the 

 hypostoma of a species of Lichas. 



