those of the Istiophoridae. The large rostrum is simi- 

 lar in size and shape to that of the genus Makaira 

 except that it is more flattened at its base. In cross- 

 section, the xiphiorhynchid bill (Fig. 1 1) has a cen- 

 tral longitudinal nutrient canal as well as two or more 

 pairs of lateral nutrient canals. Istiophorids have 

 only one pair of lateral longitudinal canals and lack a 

 central canal. Xiphiids have a central longitudinal 

 canal with only one pair of lateral canals. In short, 

 this new species of Xiphiorhynchus seems to be in- 

 termediate to both the Istiophoridae and the 

 Xiphiidae. 



The Xiphiidae has a poor fossil record and this 

 may be due to the poor ossification of its bones. 

 Leriche (1910) identified one caudal vertebra from 

 the Oligocene of Belgium as Xiphias rupelensis and 

 it is similar to the hypural plate of Xiphias gladius. 

 Most references to fossil Xiphiidae refer to the 

 "Cylindracanthus group" or to the Istiophoridae. 

 Recently Shelton Applegate of the Los Angeles 

 County Museum of Natural History found a rostrum 

 in the Eocene of Mississippi. It is 750 mm long, is 

 depressed, and has a cross section at its base similar 

 to a double-bladed axe. Distally the sharp lateral 

 edges become blunt and the edge has a scalloped 

 margin. Although the rostrum is unique, I strongly 

 feel that it belongs to an yet unknown xiphiid. 



In summary then, the classification of billfish 

 should be: 



ORDER PERCIFORMES 



SUBORDER XIPHIOIDEI 



FAMILY ISTIOPHORIDAE (lAcestrus, 



Brachyrhynchus , Istiophorus, Makaira, Tet- 



rapturus) 



FAMILY XIPHIORHYNCHIDAE 



(Xiphiorhynchus) 



FAMILY XlPHUDAE(Xiphias, and unde- 



scribed Eocene genus) 



XIPHIOIDEI INCERTAE SEDIS 



FAMILY PALEORHYNCHIDAE (En- 

 niskillenus, Hemirhynchus, Homorhynchus, 

 Paleorhynchus, Pseudotetrapturus) 

 FAMILY BLOCHIIDAE (Blochius, 

 ? "Cylindracanthus group") 



Figure 12. — Two vertebrae of Xiphiorhynchus sp. from 

 the Eocene of Mississippi. A. Lateral view of abdominal 

 vertebra. B. Ventral view of abdominal vertebra. C. 

 Lateral view of caudal vertebra. D. Ventral view of caudal 

 vertebra. 



40 



