30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 85 



(b) that they were of a very deHcate structure and readily destroyed ; 



(c) that when preserved they were hkely to be distorted and displaced 

 by compression in the shale and could only be seen from the ventral 

 side of the flattened carapace when they projected beyond the margin 

 and were outlined on the shale. At first I thought that the eyes were 

 situated on the carapace just within the line of its union with the 

 large antero-lateral spines. Later I re-examined all the specimens 

 showing the eyes, and found two that indicated that the visual surface 

 of the eye was on one side of the suture separating the spines from 

 the carapace, and the cap or palpebral lobe on the other, and one that 

 (juite clearly indicated that it was attached to the proximal end of the 

 great spines, the latter being equivalent to the free cheeks of the 

 trilobite. The interpretation of this is that the visual surface of the 

 eye was attached to the great spine outside of the suture that outlined 

 the spine from the carapace, and that the cap or palpebral lobe of the 

 elevated visual surface of the eye was attached to the carapace as 

 in the trilobites with elevated eyes and free cheeks. 



It is difficult to determine the extent of the elevation of the eye 

 above the carapace, but from its inconspicuous position in the fossil 

 state I strongly suspect that it was only slightly raised and that its 

 field of vision was largely forward and downward ; this would be in 

 accord with the needs of a small, active, free-swimming animal that 

 spent little time on the bottom. 



Among the trilobites the eye of Dciphon forhesi Barrande ' is at the 

 proximal end of a large genal spine forming the free cheek, and the 

 great eye of Bohemilla sinpcnda Barrande ^ occupies nearly the entire 

 width of the proximal end of the free cheek which is extended into a 

 long strong spine. 



Digestive organs. — The intestinal canal extends from the posterior 

 margin of the labrum back to the small, platelike termination of the 

 body ; it is contracted a little opposite the line of union of each of the 

 segments (see figs. 6, y, and 9, pi. 22) ; anteriorly the intestine widens 

 out between the labrum and carapace to form what may have been 

 the stomach ; the narrow canals of the dorsal lobes passed into the 

 space between the carapace and labrum and probably entered the en- 

 larged intestinal canal as did the canals of the antero-lateral spines 

 which appear to pass without interruptions through the close sutures 

 that unite them with the carapace; tiie canals of the postero-dorsal 

 lobes may re])resfnt the shell-gl.'uuls or excretory organs of the recent 

 Apodidae. 



' Syst. Silur. de Bolieiiic, vol. i, pi. 2B, fig. 4, 1852; suppl., pi. _', fig. 19, 1872. 

 'Idem, vol. i, Suppl., pi. 14, fig. 30. 



