248 Annals of the Carnegie Museum. 



Thaleops ovata Clarke, 1897, Paleontology Minnesota, Vol. Ill, pt. 2, 



p. 716, figs. 25-28. 

 Not Th a leops ovatus Raymond, 1902, Bulletin American Paleontology, 



Vol. Ill, PL 18, fig. 9. 

 Not Thaleops ovata Raymond, 1905, Annals Carnegie Museum, Vol. 



IH, P- 35 2 , P1 - 1 3, fi g- 5- 



This species is well known and has been so frequently described 

 that it is only necessary to add here a description of the genal spines. 

 As shown by the figures, these spines are strong, rather heavy, with a 

 prominent keel on the upper surface, making the spine triangular in 

 section. This character of the genal spines is especially well shown 

 on specimens from Ottawa, and is also exhibited by Conrad's types, 

 which are preserved in the American Museum of Natural History, 

 New- York City. 



Entire specimens of this species are very rare in the vicinity of 

 Ottawa, while fragments are very common. The entire specimens 

 vary in length from 19 to 47 millimeters. 



Thaleops arctura (Hall). 



(Plate LXI, figure 8.) 



lllcenus arcturus Hall, 1847, Paleontology of New York, Vol. I, p. 



23, PL 4 bis, fig. 12. 

 lllcenus arcturus Emmons, 1855, American Geology, Vol. I, pt. 2, 



P- 235, PL 3, fig. 12. 

 Thaleops arctura Clarke, 1897, Paleontology of Minnesota, Vol. Ill, 



pt. 2, p. 718. 

 Thaleops ovatus Raymond, 1902, Bulletin of American Paleontology, 



Vol. Ill, PL 18, fig. 9. 

 Thaleops ovata Raymond, 1905, Annals Carnegie Museum, Vol. Ill, 



P- 35 2 , PI- J 3> fig- 5- 



At the time this species was described by Raymond in the articles 

 cited above, he was unable to compare the Chazy specimens with any 

 well-preserved specimens from the Trenton and none of the pub- 

 lished descriptions allude to the rather minor characters which sep- 

 arate Thaleops arctura from Thaleops ovata. In Thaleops ovata, the 

 palpebral lobes are depressed, and are at the same level as the sum- 

 mit of the fixed cheeks, while in Thaleops arctura the eyes are much 

 more prominent and rise at an angle of about 30 degrees with the 

 surface of the fixed cheeks. Furthermore, the genal spines in the 



