VERTEBKATA. 117 



end, more or less bent, with sharp opposite margins, which 

 might well be lingual teeth of Gastropods, acetabular hooklets 

 of Cephalopods, or teeth of cartilaginous fishes. Against the 

 latter determination is the minute size of the "Conodont" 

 bodies; their observed structure presents concentric conical 

 lamellae of a dense structureless substance, containing minute 

 nuclei or cells. 



In some specimens the base is abruptly produced and 

 divided from the body of the booklet by a constriction — a 

 form unknown in the teeth of any fishes, but presented by 

 certain lingual teeth of Gastropods — e.g., the lateral teeth of 

 Sparella. In other Conodonts the elongated base is denticu- 

 late or serrate, as in the lateral teeth of Buccirmm and Ghry- 

 sodomm. It is improbable, however, that they belong to any 

 conchiferous toothed Mollusk, the shells of such being wanting 

 in the deposit where the Conodonts are most abundant. 



The more minute hooklets have a yellowish, transparent, 

 horny appearance ; the larger, perhaps older ones, present a 

 harder whitish appearance. Their analysis by Pander yielded 

 " carbonate of lime," carbonic acid being evolved by appli- 

 cation of dilute nitric acid, and oxalic acid producing an 

 obvious precipitate. Some English analysts have believed 

 that the Conodonts yielded a trace of phosphate of lime. 



The detached condition of the hooklets, and the integrity 

 of the thin border of the basal pulp-cavity, indicate that they 

 have not been broken away from any of those kinds of 

 attachment to a bone which the minute villiform teeth of 

 osseous fishes woidd shew signs of. The Conodonts have 

 been supported upon a soft substance, such as the skin of a 

 mollusk or worm, the mucous membrane of a mouth or 

 throat, or the covering of a proboscis. 



In comparing the Conodonts with the teeth of fishes, they 

 present most resemblance to the minute conical recurved teeth 

 of the genus Rhinodon of Smith : they more remotely resemble 



