376 REPORT— 1869. 



additional diiSculty in determining their affinities. They are generally either 

 lustrous or horny in their appearance, or dull, according to the matrix in 

 which they are found. My collection of them affords certain well-marked 

 recurrent types, which enable a certain amount of classification to be given 

 to them ; and though, taking the group as a whole, their forms are about as 

 eccentric as can be imagined, they still do not appear to pass one into 

 another. The simplest form is almost identical in shape with that of a 

 minute conical fish-tooth. Next comes another, not unlike the central cusp 

 of a hyboid tooth, with lateral bosses at the base. Another group possesses 

 an arched base, the simplest form in which has an elevated central curved 

 tooth, with a smaller projecting tooth on cither side. A second form has 

 four elevated slightly curved teeth, with smaller teeth at the sides and in 

 the interspaces, whilst a still more elaborate one possesses a single elevated 

 central curved tooth, with about twelve regularly arranged, close-set smaller 

 ones on either side. A third group have their teeth arranged on an irregular 

 or waved base, the forms of which are almost too eccentric for description. 

 In one there are nine curved teeth, arranged somewhat symmetrically, gra- 

 duating in height to the centre, but with a much larger fang at one end ; 

 a second form has five tapering teeth, followed by four others, much more 

 depressed and extended beyond the base. One kind presents a miniature 

 representation of the jaw of Ehizodus, with large teeth widely separated, 

 and irregularly dispersed small teeth within. A remarkable form possesses 

 a long curved tooth at one end, throwing off a semicircular spur, which passes 

 under a base-line, on the top of which follow numerous small depressed re- 

 gular teeth, the next two becoming much elevated, whilst the last is still 

 more so, extending much beyond the basal end. Another series, which has a 

 lengthened straighter base-line, is furnished in some instances with ser- 

 rations as close-set and minute as are the bristles on an insect's limbs. 

 In the width, form, and curvature of the teeth, these present various modi- 

 fications. Although in the above short descriptions I have by no means 

 exhausted the variety they present, I shall only notice here another kind, 

 which is the most abundant, and similar to one previously found in the Ludlow 

 bone-bed. This presents a somewhat club-shaped form, the thicker end 

 having in the centre a depression, bounded on the margin by a raised edge, 

 furnished with very minute serrations, which are united at about the centre 

 of the body, and are continued beyond in a very thin slightly curved handle, 

 which is also furnished with close comb-like teeth. A familiar illustration 

 of this Conodont would be that of an old-fashioned rat-trap. Its base pos- 

 sesses a somewhat triangular hoUow, indicating that it might have been 

 attached at this part to some soft body. 



These curious fossils were first found by Pander, in Silurian beds in 

 Russia ; and considering that they belonged to and were the teeth of fish, 

 he created 13 genera and 56 species, according to the forms they presented. 

 In almost every instance the specimens I have found differ from those of 

 the Sihirian beds, and present much more diversity. Several of the Russian 

 varieties were, for the fii'st time, noticed in the Ludlow bone-bed by Dr. 

 Harley, who, in a paper in the 'Geological Journal,' 18G1, p. 549, suggests 

 that they may be minute spines attached to the tail of a crustacean, such as 

 Ceratiocaris. 



They have more recently been noticed by Professor Owen, in a note to 

 the last edition of ' Siluria,' p. 544, in which he also points out the improba- 

 bility of their being allied to fish. He then remai'ks that certain parts of 

 small Crustacea, such as the pygidium or tail of minute Entomostraca, resemble 



