2 A. S. Woodward — Devonian Fishes, Canada. 



result of specialization. Such being the case, Protochis is a specialized 

 form of a very simple type of tooth. 



1. Protodus Jexi, sp. nov. PI, I. Figs. 1, la. 



Crown of tooth attaining a height of about OOOo, and measuring 

 0-003 in width at the base; the apical half sharply bent inwards; 

 coronal surface smooth, the lateral margins keeled, both faces convex, 

 and the outer face with an nnsymmetrically placed longitudinal ridge 

 imparting to the tooth a twisted appearance. Koot compact, stouter 

 and much less deep than the crown. 



The best-preserved specimen is shown of the natural size in 

 PI. I. Figs. 1, la, and there are four more imperfect examples in the 

 collection. The specific name is suggested in honour of Mr. Jex, 

 of Weymouth, to whose skill in collecting so many remarkable 

 discoveries of Devonian and Carboniferous fishes, both British and 

 Canadian, are due. 



Genus DiPLODUS, Agassiz. 



[Poiss. Foss. voh iii. 1843, p. 201:.] 



Teeth of this form are now known to be common to several genera 

 of primitive Elasmobranchs, already discovered in formations ranging 

 from the Lower Carboniferous to the Upper Trias. A unique speci- 

 men in the new collection of Lower Devonian fish-remains from 

 Campbellton now seems to show that the same type of tooth occurred 

 in certain Elasmobranch Fishes even in the early portion of the 

 Devonian period ; and the discovery of parts of the skeleton of these 

 ancient forms will be awaited with considerable interest. 



2. Diplodus prohJematicus, sp. nov. PI. I. Fig. 2. 



The single tooth referred to appears to be destitute of the root and 

 exhibits only the outer face of the crown. It is shown of three 

 times the natural size in PI. I. Fig. 2. The two princijml cusps are 

 well separated, unequal in size, and widely divergent ; each being 

 long and slender, somewhat tumid in the basal portion, and at- 

 tenuated distal ly. The median cusp or denticle is subulate, long 

 and slender. The gano-dentine is quite smooth. 



Though several forms of '' Diplodus " are known to occur in one 

 and the same mouth of some Pleuracanth fishes, and the recognition 

 of specific characters in detached teeth thus becomes impossible ; it 

 still seems advisable to adopt provisional names for isolated examples, 

 and the Lower Devonian tooth described above may thus be known 

 as Diplodus prohlematims. More especially does this name appear 

 to be approi)riate, as the form of the root and the microscopical 

 structure of the tooth yet remain to be determined. 



Genus Gykacanthus, Agassiz. 

 [Poiss. Foss. vol. iii. 1837, p. 17.] 

 3. Gyracanthus incnrvus, Traquair. PI. L Figs. 4, 5. 

 1890. E. H. Traquair, Geol. Mag. [3] Vol. VII. p. 21. 



A small, much arcuated, and laterally compressed spine, attaining 

 a length of about 0065. Anterior border acute ; posterior border 



