416 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



aberrant or divergent type ; the 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 oi)portunities 

 of studying and formulating by means comparison, certain structural 

 characters never before expressed. 



Description of the family Xiphiid^. 

 Family XIPHTID^, Agassiz. 



Xiphioides, Agassiz, Eecherches snr les Poissous Fossiles, v, IS43, p. 89. — Bleeker, 



Eunm. Sp. Pisc. 18*9, p. 62. 

 XijjMidw, GtJNTHER, Catalogue of the Fishes iu the British Museum, ii, 1860, p. 511 ; 



Fische des Sudsee, i, 1873-5, p. 105; Study of Fishes, 1880, p. 431.— Gill, 



Arraugement 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 {Tetraptnrinw) or naked {XipMinw). Pre- 

 raaxillaries with nasal and vomeriue bones produced in a long spear- 

 likfi snout, immovably articulated with the prenasal and maxillary. 

 Teeth rudimentary {Tefraptnriiuv) or absent {Xiplmnw). ISTa.^al bone 

 cellular at its base. Ventrals rudimentary (Tetrapturiiur), or absent 

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

 body iu young, ])ersistent {Ilistiophorm) or subpersistent, divided in 

 middle with age {Tefrapfnrns), or becoming with age subdivided into 

 two short dorsals [Xiphtina'). A similar rudimentation of anal fin iu 

 both subfamilies. Preopercular spine i>resent in young {XipJdincv), or 

 parietal and preopercular spines {Tetrapturiruv), disappearing with age. 

 Seven branchiostegals. Pseudo-branchife present. Branchioe cancel- 

 lated or reticulated. Air-bladder present, cellulated {Tetrapturus and 

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

 {Tttrapturincc)j or long, sinuous {XiphUna'). Gall-bladder free, hanging 

 at some distance from the liver. Articular processes developed from 

 the parapophyses. 



Synopsis of subfamilies. 



Ventrals present : skin with scutes : snout ronndcd: caudal keels double. 



Tktraptuhix.k, Gill. 

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



* 1875, LiJTKEX, CriR. 



Om rundnaebidea Svaerdliske, saerligt om Histiojyhorits orientalis, Schl. <^ Vidensk. 

 Meddel. Naturhist. Foreu. Kjobenhavn, 1875, pp. 1-21 -j- 1-5. 



