FISH OF THE CARBONIFEROUS PERIOD. 17 



of Asterolepis (Eich.). The base is imperfect but apparently di- 

 lated in a remarkable degree, and in its present state the lower 

 portion seems bent at a considerable angle from the curve of the 

 rest of the spine. 



Collected from the carboniferous limestone of Armagh by the 

 Rev. W. Stokes of Caius College, Cambridge, and by him pre- 

 sented to the University collection. I have associated his name 

 with this interesting form as a slight memorial of the zeal with 

 which he has collected those remains, and the liberality with 

 which he has made them available for public instruction. 



Leptacanthus junceus (M'Coy). 



Sp. Char. Nearly straight, about li line wide ; section semiel- 

 liptical ; sides nearly convex, meeting in front to form a sharp 

 anterior edge, and converging behind to a narrow posterior 

 sulcus, bordered on each side by a row of strong, conical, 

 downward-curved teeth, little longer than wide, and about the 

 width of their base apart ; each side with about seven longi- 

 tudinal, narrow, equal, thread-like ridges, twice their diameter 

 apart, and having between each pair two or three obsolete 

 longitudinal striae. 



Rare in the black beds at the top of the carboniferous lime- 

 stone of Derbyshire. 



[Col. University of Cambridge.) 



(Cestraciontes — Teeth.) 



Psammodus canaliculatus (M'Coy). 



Sp. Char. Tooth oblong, generally about twice as long as wide, 

 the two long sides straight and parallel, one of the short sides 

 or ends very convex, the other equally concave (for articula- 

 tion) ; the crown of the tooth concave along the middle, the 

 two long margins being prominent and rounded ; there is ge- 

 nerally a considerable hump-like elevation near the convex 

 end ; surface roughly wrinkled transversely, the ends generally 

 more or less rudely plicated longitudinally. 



This remarkable tooth is much allied to the P. rugosus (Ag.), 

 but is strongly distinguished by its ends being formed for arti- 

 culation, one convex and the other concave, instead of being 

 straight as in that species ; also by the strong longitudinal plica- 

 tion of the surface near the ends, and the peculiar, curved, 

 swelling near the convex extremity. When the ends are wanting 

 it is distinguished by its mesial concavity (the other being con- 

 vex), and by the minute rugae of the surface running across 

 instead of in the direction of the length. When much worn the 



