Pisczs. | UPPER PALAOZOIC VERTEBRATA. 631 
I figure as above a longitudinal, slightly curved, row of teeth, found in sitw, of this latter form ; they gra- 
dually diminish in size from behind, forwards. Agassiz figures a similar row of three teeth, of the second or 
mammillaris form. The transversely oval forms vary from two lines to six in length, and are nearly twice as 
wide as long. 
Position and Locality.—Not very uncommon in the lower carboniferous limestone of Armagh. 
Explanation of Figures.—P1, 3.1. fig. 17, group of four teeth in sitw (Captain Jones’s collection), natural 
size; fig. 17 a, profile of ditto. 
HELODUS MAMMILLARIS (4g. name only), PI. 3. I. fig. 16. 
Dese.—Crown very much elongated, narrow, abruptly pointed at each end, having a moderately large 
rounded, abruptly tumid, gibbosity, rather nearer to one end than the other, and sometimes haying an obscure 
beaklike projection, with an underlying vertical area, over one of the long, lateral margins; short end even and 
pointed ; long end with one or two very faint, small, secondary gibbosities. Surface of the large prominent 
boss coarsely granulo-punctate, the punctations being finer, and often obscured by a polished surface of 
ganoine, on the ends. Average length seven lines, greatest width two lines, height of crown, one and a half 
lines. 
This species of M. Agassiz is founded on specimens which scarcely can be said to differ, except in size, 
from his H. subteres, and I expect that additional specimens will prove their perfect identity. The more 
slender form is the only difference from his H. gibberulus, which I think will also be found to belong to the 
same species. 
Position and Locality.—Rare in the lower carboniferous limestone of Armagh. 
Explanation of Figures.—P\. 3.1. fig. 16, natural size; fig. 16 @, profile of ditto. 
HELODUS PLANUS (Ag. name only), PI. 3. I. figs. 12 to 15. 
Desc.—Tooth irregularly elongate, oblong, with a slight oblique diagonal twist, narrowed, and rotundato- 
subtruncate at the ends, between which the crown widens; widest nearer to one end than the other; surface 
flattened obtusely, slightly convex, very coarsely granulo-punctate, while parts of some punctate examples and 
the whole of others are polished and smooth; sides of the crown and osseous base strongly plicated vertically. 
Average length about ten lines, greatest width about five lines, depth of crown about two lines, depth of root 
one and a half lines. 
The characteristic oblique torsion of this species inclines Captain Jones to class it with the Cochliodus 
magnus (see Portk. Geol. Rep. p. 462). 
Position and Locality—Common in the lower carboniferous limestone of Armagh; rarer in the carboni- 
ferous limestone of Kendal, Westmoreland; rare in the lower carboniferous limestone of Lowick, Northum- 
berland. 
Explanation of Figures—PI. 3. I. fig. 12, narrow oblong specimen, natural size; fig. 12, profile of 
same specimen ; fig. 18, shorter oblong specimen; fig. 14, irregular subrhombic, worn, punctured specimen ; 
fig. 15, subclavate specimen. 
Hetopus rupis (M*Coy). Pl. 3.K. fig. 4. 
Ref—MCoy, Ann. Nat. Hist. 2nd Series, Vol. II. p. 1238. 
Dese.—Irregularly oblong, subquadrate; sides steep, irregularly nodulose, or undulato-plicate; crown 
irregularly gibbous, the highest point a little nearer one end than the other; surface polished, coarsely punc- 
tured. Length seven lines, width four and half lines, height two and half lines. 
[wasc. 111.] 4M 
