Families of Tehosiean Fishes. 187 



Post-temporal distinctly forked ; praecaudal ver- 

 tebrae with hsemal arclies ; dorsal rays all 

 spinous ; caudal fin distinct 11. Pholididce. 



Post-temporal distinctly forked ; prseaaudal ver- 

 tebrte with transverse processes; dorsal rays 

 all articulated, or a iew of the posterior 

 spinous ; no distinct caudal 12. Zoarcidcs. 



Post-temporal forked, aukylosed to the skull ; prse- 

 caudal vertebrae with transverse processes ; no 

 spines ; no distinct caudal 13. CongrogadidcB. 



B. Ventrals mental (just behind the chin) ; no spines. 



14. Ophidiid(e. 



III. Pectoral rays attached to an undivided cartilaginous plate repre- 

 senting the pterygials ; ventral tins jugular, reduced to a filament 

 formed of two adnate rays ; fins without spines. 



15. Podatelidce, 



Division IX. T^NIOSOMI. 



Exceedinglj compressed, more or less elongate, often 

 ribbon-like fishes of doubtful affinities, probably related to 

 the eailier Acanthopterygians, the ventral fins, when well 

 developed, comprising as many as 7 to 9 rays. Dorsal fin 

 extending from the head to the end of the tail, its rays 

 simple (separable into lateral halves), the anterior often 

 prolonged ; anal fin very short or absent. Pectoral fin with 

 iiorizontal, or nearly horizontal, base, the rays supported by 

 the scapula and by three short pterygials, all three, or two 

 at least, of which are related to the coracoid. Ribs small 

 and slender, or absent. Post-temporal simple and solidly 

 attached to the skull. Scales minute or absent. 



Deep-sea or pelagic fishes from the Atlantic and Mediter- 

 ranean and from the Pacific ; specimens are rare in collec- 

 tions and the life-histories are still very imperfectly known, 

 although it has been ascertained that great changes of form 

 take place with growth. 



Only two families : — 



Mouth very protractile ; ventral fins more or less 

 developed, with 6 to 9 rays, or reduced to a 

 single long ray ; no anal fin ; vent about the 

 middle of the body ; caudal rays, if present, 

 divided into two fascicles, the upper sometimes 

 much prolonged and directed upwards 1. Trachypteridce, 



Mouth moderately protractile ; ventrals very small, 

 if distinct, with 4 or 5 rays ; body-cavity ex- 

 tending nearly the whole length of the much 

 elongate body, the vent very far back and fol- 

 lowed by a short anal fin ; caudal fin small, 

 not divided 2. Lop}iotid(t. 



