1870.] 9 [Bliss. 



and with the dermal plates, serves to give the necessary support to 

 the apparatus. When the fish would erect the spine of the fin, the 

 muscles attached to the anterior face of the little forked bone or 

 rider, contract, pulling the bone forward and downward on the 

 rounded crest of its interneural. The articulating facet, upon which 

 rest the arms of the large spine, acting as a fulcrum, the ligaments 

 which pass from the posterior edge of the rider to the base of the 

 spine, cause it to rise with the forward and downward movement of 

 the rider. When erect, the spine cannot be lowered by pressure 

 upon it from above; any attempt to thus depress it serves only to 

 pull the rider more closely against the crest which now stands be- 

 tween it and the large spine. By this means the fish is enabled to 

 inflict so severe a wound as to render him a formidable antagonist. 

 In order to lower the spine, the muscles connecting the arms of the 

 rider with the anterior edge of the articulating facet contract, pull- 

 ing the rider up the crest, which, at the same time, allows the large 

 spine to be lowered by appropriate muscles attached to the posterior 

 edge of its arms. 



Geoffroy St. Hilaire, in his paper on the analogy of the fishing 

 filaments of Lophius piscatorius with the first rays of the dorsal fin 

 in the Siluroids, published in the Memoirs du Museum d' Histoire Na- 

 turelle (Tom. xi, p. 132), gives a detailed account of this fin appa- 

 ratus, and there shows for the first time, that the little forked bone, 

 which had escaped the notice of former naturalists, is truly a spine 

 of the dorsal fin. He describes it, however, as the first spine of the 

 fin, while, as previously mentioned, I am led to regard it as the 

 second, believing that the dermal plate supported by the first inter- 

 neural is really the first spine. 



Cuvier, also, in his " Anatomie Comparee" (Tom. I, p. 126), al- 

 ludes to this peculiar articulation of the large dorsal spine in the 

 Siluroids ; and in his Valenciennes and " Histoire Naturelle des Pois- 

 sons" (Tom. xiv, pp. 310-322), gives a very brief description of 

 this fin structure in the diagnosis of the family of Siluroids. 



The third anchylosed centrum is quite short, not much larger than 

 the first. Its neural spine is broad and short, and unites with the 

 neural spines in front of and behind it, as well as with the inter- 

 neural spine belonging to the first branched ray of the dorsal fin. 

 The parapophyses of this centrum consist of large, porous, rounded 

 excrescences, affording attachments to the posterior portion of the 

 air-bladder. They are true apophyses, and near their bases afford 



