454 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
Teeth, large, laterally elongate; outline irregular, length about double the 
width, broadest in middle, tapering slightly and unevenly towards each lateral 
extremity : length 1:2 inch; height of central cone ‘45 inch; breadth ‘6 inch, 
diminishing at one lateral extremity to three-quarters, and at the other to half, 
the greatest breadth ; the broader lateral extremity may be either to the right or 
left of the central cone. Crown: central cone moderately elevated, laterally broad, 
obtusely pointed: transversely somewhat beaklike, a ridge extends from centre of 
the cone down each side, it is sinuous and slightly produced to form two or three 
small minor cones, towards each lateral extremity. Posterior face, depressed from 
the ridge of the crown to its posterior margin forming a deep concavity ; anterior 
surface, convex; coronal surface, coated with thick, dark, beautifully polished 
enamel, generally perfectly smooth, but in a few specimens covered with projecting 
pustulate dots. Posterior ridge separating the crown from the base, broadly 
expanded, margin concave. Anterior ridge, sinuously convex, broadly expanded, 
Occasionally four or five concentric plice extend along the anterior and posterior 
ridges, but in the majority of specimens they are not present. Base; °3 of an 
inch in depth ; laterally, equally extended with the crown, descending obliquely 
from the posterior portion of the tooth, strong, fibrous in structure. 
Helodus tenuis, Davis. 
(PL TID, ines, 83, 444) 
Chomatodus cinctus, Ag., pars. 
Teeth, long, transverse section lateraJly much elongated, narrow, elliptical, 
pointed at each extremity. Length to 1:0 to 1:2 inch, breadth, °3 to -4 inch, height 
of central cone °35 of an inch. Crown: central cone, elevated, more or less sharply 
pointed and thin ; anterior and posterior faces form a ridge at an acute angle 
extending from the summit of the cone laterally in each direction and terminating 
in an acute point. Ridge sometimes straight, in others sinuous; free from minor 
cones. Anterior surface, convex. Posterior surface, deeply concave, summit of 
cone recurved. Coronal surface, enamelled ; summit of ridge smooth, probably 
with attrition during mastication, sides of ridge either coarsely punctate or pustulate. 
Posteriorly a ridge separates the crown from the base, anteriorly the surface of the 
crown is continued down into the base; there are no concentric folds. Base, 25 
inch in depth, slightly produced anteriorly, rather more widely expanded than the 
crown, strong and fibrous. 
This tooth is easily distinguished from the species last described by its generally 
more attenuated form and the acuteness of the coronal ridge, extending along the 
centre of the tooth and its somewhat recurved apex. 
This species was included by Professor Agassiz in the genus Chomatodus, but 
the characteristic on which he lays greatest emphasis, the concentric folds near the 
base of the tooth, are absent. 
