216 ACANTHOPTERYGII. 



Ninth group Acanthopterygii tseniiformes. 



Body riband-shaped. Dorsal fin extending the entire length of the hack : 

 anal absent : caudal, when present, rudimentary, or not in the longitudinal axis 

 of the body. 



Family, XXIII TRACHYPTERHLE (paet), Swainson. 



Tamioidei, pt. Cuvier. Gymnetridce, Gray. 



Branchiostegals six : pseudobranchise present. Body elongated and strongly 

 compressed. Gill-openings wide: gills four. Eyes lateral. Cleft of mouth 

 slight. Dentition feeble. A single dorsal fin occupying the whole length of the 

 back, and which may have a detached anterior portion, the whole composed 

 of rays which are neither articulated nor branched. Anal absent. Caudal 

 not in the longitudinal axis of the fish or else rudimentary: ventrals, when 

 present, thoracic. Scales absent. Pyloric appendages numerous. Vertebrae 

 many. Bones soft. 



Among the fishes occasionally taken off the British coasts, there are'Jfew 

 pelagic or abyssal forms that have given rise to so many theories and conjectures 

 as the " riband fishes." While their life history, and even their very external 

 appearance are not thoroughly elucidated. Generally of a brilliant silvery lustre 

 they have been mixed up with the similarly coloured Trichiiiridce, of which we 

 possess species of two genera, Lepidopus and Trichiurus, already described (pp. 153, 

 150). Some have been credited with being the veritable sea serpent (see Regalecus, 

 page 223) both while in the ocean and also when observed in a pool on shore. 

 One form at least (see Trachypterus, page 219) is a slow swimmer and lies at the 

 bottom of the sea reclining on one side as occurs in the flat fishes (Pleuronectidce) . 

 None have been recorded as captured by the deep sea dredge, but their remains 

 are by no means rare. The difficulty of obtaining unmutilated specimens is very 

 great, due to the brittleness of their bodies, the fragility of their rays, and the 

 soft character of their thin and porous bones. While their soft flesh rapidly 

 decomposes after death. Many young ones are said to have been taken near 

 the surface. 



The British genera as at present known are restricted to 1, Trachypterus, caudal 

 fin present : 2, Regalecus, caudal fin absent. 



Professor Gill likewise suggested that a Cuban fish belonging to a recently 

 recognized genus, Euoxymetopon, might be identical with an example captured in 

 Scotland in 1812, and Dr. Gunther, in his Introduction to the Study of Fishes, 1880, 

 observes at page 435 respecting the genus Euoxymetopon that " a specimen has 

 been known since the year 1812 : it was found on the coast of Scotland and 

 described as Trichiurus leptums." At page 221 I have given my opinion that the 

 fish alluded to is a Regalecus, and cannot be identical with the new West Indian 

 form. 



Geographical distribution. Abyssal forms found to very high latitudes and 

 most numerous in the Atlantic, Mediterranean and North Pacific Ocean. While 

 a solitary example has been taken on the coast of India: also at the Mauritius 

 and Eastern Pacific, as well as off New Zealand and the west coast of South 

 America. 



