416 PKOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



aberrant or divergent type ; tlie round-billed species, provided with ven- 

 tral fins, especially those of the genus Histiophorus, being the most 

 typical and representative of the group.* 



Representatives of all the genera of the sword-fish family occurring 

 in the waters of the United States the writer has had opportunities 

 of studying and formulating by means comparison, certain structural 

 characters never before expressed. 



Description of the family Xiphiid^. 

 Family XIPHIIDJ^:, Agassiz. 



XipMoides, Agassiz, Recherclies snr les Poissous Fossiles, v, 1843, ji. 89. — Bleeker, 



Enum. Sp. Pise. I8S9, p. 62. 

 Xiphiidce, Gunther, Catalogue of the Fishes iu the British Museum, ii, 1860, p. 511 ; 



Fische des Siidsee, i, 1873-5, p. 105; Study of Fishes, 188Q, p. 431.— Gii.l, 



Arrangement of the Families of Fishes, 1872, j). 8 (name only). — Day, Fishes 



of India, i, 1876, p. 198, 



Diagnosis of family. 



Scombroid fishes, with elongate, compressed bodies, covered with 

 elongate scale-like scutes {Tetrapturinm) or naked {Xlpliiinw). Pre- 

 maxillaries with nasal and vomerine bones produced in a long spear- 

 like snout, immovably articulated with the prenasal and maxillary. 

 Teeth rudimentary {Tctrapturina) or absent {Xiphiino'). Xasal bone 

 cellular at its base. Yentrals rudimentary {Tetrapfurina'), or absent 

 {Xiphiinw). A single dorsal, extending nearly the whole length of the 

 body in young, jiersistent {Histiophorus) or subpersistent, divided in 

 middle with age ( Tetrapturus), or becoming with age subdivided into 

 two short dorsals {Xiphiina'). A similar rudimentation of anal fin in 

 both subfamilies. Preopercular spine present in young {Xiphiina'), or 

 l^arietal and preopercular spines {Tefrapturinw), disappearing with age. 

 Seven branchiostegals. Pseudo-branchife present. Branchins cancel- 

 lated or reticulated. Air-bladder i)resent, cellulated {Tetrapturus and 

 Histiophorus {?)), or simple {Xiphiina'). Intestine short, not sinuous 

 {Tetrapturinw), or long, sinuous {Xiphiinw). Gall-bladder free, hanging 

 at some distance from the liver. Articular processes developed from 

 the parapophj^ses. 



Synopsis of subfamilies. 



Ventrals present : skin with scutes : snout rounded: caudal keela double. 



TetrapturiXyE, Gill, 

 Ventrals absent: skin scaleless: snout flat: caudal keel single.. XiPHiiisriE, Swainson. 



* 1875, Lutken, Chr. 



Om rundnrebides Svaerdfiske, saei-ligt om Histiophorus orientaUs, Schl. <^ Vidensk. 

 Meddel. Naturbist. Foren. Kjobenhavn, 1875, pp. 1-21 ^- 1-5. 



