4 Mr. F. M'Coy on some new Fossil Fish 



are distinguished by their circular section, and wide, simple pulp- 

 cavity, which latter distinguishes it from nearly all palaeozoic teeth 

 except the old red sandstone genus Cricodus (Ag.), from which 

 it is known by its more slender conical form, and wanting the 

 strong longitudinal ridges of the surface, as well as possessing 

 the distinctly denned enamel layer, which has all the appearance 

 of having been secreted by a distinct organ, and is quite different 

 from the condensed dentine which forms the false enamel of 

 most fish-teeth. 



Centrodus striatulus (M'Coy). 



Sp. Char. Tooth about half an inch long and 1| line in diameter 

 at base ; conical, gradually tapering to the pointed apex, with 

 a slight backward curve ; about one-fifth of the surface towards 

 the apex perfectly smooth ; the remainder, under the lens, is 

 minutely and irregularly striated longitudinally. 

 This remarkable tooth, the only species I as yet know of the 

 genus, seems to present all the characters, external and micro- 

 scopic, of a true Saurian reptile ; and when we compare it with 

 Herman von Meyer's genus Pistosaurus, for instance, of the 

 Laineckerberg Muschelkalk and other allied Saurians, the resem- 

 blance is such as to caution geologists against laying too much 

 stress on the supposed first appearance of reptiles in the mag- 

 nesian limestone, when drawing a line which would separate this 

 group from the palaeozoic rocks below. 



Common in the bituminous carboniferous shale of Carluke, 

 Lanarkshire. 



(Col. Cambridge University.) 



Colonodus (M'Coy), n. g. 

 (Etym. fcwXov, ilia, and 68ovs, dens.) 

 Gen. Char. Tooth elongate-conic, very gradually tapering, sec- 

 tion round near the base, becoming trigonal towards the apex ; 

 front even, sides impressed with short, alternating, transverse, 

 wrinkle-like furrows ; enamel-like surface smooth, highly 

 polished, longitudinally marked with few, distant, minute im- 

 pressed striae ; it terminates obliquely at the base, the edge 

 being slightly notched or wrinkled ; base forming a short, 

 slightly dilated round disc, placed obliquely to the axis of the 

 tooth, and extending farther behind than in front, truncated 

 below and of a coarse osseous texture : medullary cavity about 

 one-third the diameter of the tooth, cylindrical, from which, 

 under the microscope, the flexuous, distant calcigerous tubes 

 are seen to radiate directly to the surface, towards which they 

 become gradually finer and closer. 

 This tooth is not unlike a bit of small intestine tied at the end, 



