Cryptolithus tesselatus Green 



(Trinucleus concentricus Hall) 



(See pi. 34) 



I, 2 Lateral views of two interior casts of median eye tubercles, 

 showing the upper smooth, glossy, lenslike body, the pitted 

 surrounding surface, and the minute tubercle in front (to the 

 right in figure) of the eye tubercle, x about ioo. 



3 Thin longitudinal section through interior cast of glabella, show- 



ing interior cast of eye tubercle and anterior tubercle (at a), 

 x 50. 



4 Thin section of interior cast of eye tubercle, x 250, showing the 



inferior carbonaceous line of the lenticular body. 



Figures 3 and 4 camera lucida outlines by author. 



5 Section through crust, covering the median eye tubercle, show- 



ing its thinning in tubercle, enlarged x 75. 



6 Right half of cephalon, to show the posterior portion of facial 



suture, x 5. ' 



7 Exfoliated cranidium, showing interior cast of eye tubercle and 



frontal portion of facial suture. Space between eye tubercle 

 ' and anterior tubercle draAvn too small, x 5. 

 Trenton limestone, Boonville, N. Y. 



Cryptolithus (Trinucleus) ornatus (Sternberg) 



8 Specimen showing posterior facial sutures. (From Barrande) 



Asaphus expansus (Linn.) 



9 Section through median eye tubercle, showing thinning of crust 



above tubercle, x 15. 

 Ordovician ( Glaukonitkalk B 2 b). Wolchow river, Gouvern. 



Petersburg, Russia. 

 All the originals, except that of figure 8, are in the New York 



State Museum. 



