298 PROCEEDIXGS OF THE NATIONAL MUSEUM. vol.52. 



be theoretically associated with the same genus. A somewhat dif- 

 ferent view has been expressed by the present writer/ who suggests 

 that the Cretaceous fans may have belonged to Protospliyraena or some 

 similar foi-m, and that the Tertiary fans, which differ from the Cre- 

 taceous in having the terminal centrum attached, properly belong to 

 swordfishes. 



In accordance with this latter interpretation, the large fan which 

 is shown in plate 16, figure 3, from the Phosphate Beds of South Caro- 

 lina, may be provisionally assigned to Xipliias, and the detached 

 tooth of 7. mira Leidy shown in plate 11, figure 2, from the Ripley 

 Group (Cretaceous) near Dumas, in Tippah County, Mississippi, 

 should be assigned to a different taxonomic position. Cope's con- 

 jecture that the teeth of Ischyriza indicate affinity with the Esocidae 

 is accepted by O. P. Hay and others, and seems plausible. The type 

 of 7. mira, together with other specimens from New Mexico, are pre- 

 served in the American Museum of Natural History 



EXPLANATION OF PLATES. 



Plate 1. 



Eeteracanthus uddeni Lindahl, p. 245. 



Head-spine, natural size. Devonian (Cedar Valley limestone) ; Johnston County, Iowa. 



Plate 2. 



Fig. 1. Dinichthys tuberculatus (?) Newberry, p. 249. 

 Dorsomedian plate, natural size. Devonian (Chemung); Warren County, Pennsyl- 

 vania. 



Fig. 2. Sauriptems taylori Hall, p. 252. 



Naturally associated cranial roofing plates, natural size. Devonian (Catakill); near 

 Blossburg, Pennsylvania. 



Plate 3. 

 Physonemus gemmatus (Newberry and Worthen), p. 263. 

 Spine, X |. Mississippian (Keokuk limestone); near Keokuk, Iowa. 



Plate 4. 

 _ Physonemus gemmatus (Newberry and Worthen), p. 263. 

 Spine, X §. Mississippian (Keokuk limestone); near Keokuk, Iowa. 



Plate 5. 

 Figs. 1 and 2. Physonemus arcuatus M'Coy, p. 264. 

 Two spines natural size. Mississippian (Keokuk limestone); Keokuk, Iowa. 



Fig. 3. Physonemus gemmatus (Newberry and Worthen), p. 264. 

 A much weathered, arcuatespine, naturalsize. Pennsylvanian ; nearSanSaba, Texas. 



Maryland Geol. Survey, Eocene, 1901, p. 111. Miocene volume, 1904, p. 93. 



