roCUUOUONTlD.E. 
181 
Psephodus Isevissimus (Agassiz). 
1838. Helodus laiiissimm, L. Agassiz, Poiss. Foss. vol. iii. p. 104, pl.xiv. 
figs. 1-14 {non fig. 15). 
Type. Detached teeth and dental plates ; Bristol iluseum (in 
part). 
A small pjjccies, tlie “ upper ” dental plate measuring about 
0 013 antero-posteriorly. Inner margin of “upper” plate nearly 
straight anteriorly for more than half its length, then sharply 
bent upwards almost at right jingles and equally straight ; coronal 
contour raised into a prominent narrow ridge along a line connecting 
the bend of the inner border with the jiosterior extremity of the 
outer border. “ Lower ” dental plate gently and more uniformly 
rounded than the “ upper inner margin very slightly curved. 
The “ upper ” dental plato is shown by Agassiz, loe. cit. fig. 13, 
but the specimen Ls imperfect and the drawing scarcely accurate ; 
the “ lower ” plate is apparently the original of fig. 14, loc. cit., and 
exhibits two small flattened teeth (erroneously shown as one long 
tooth) adjoining its postero-lateral margin. The original of fig. 15, 
loc. cit., is very suggestive of Tomoilns, and caunot be associated 
with P. Irn’issimus upon present evidence. It is also uncertain 
whether man}’ of the so-called anterior teeth of this species are 
correctly so determined, some being very large and perhaps belonging 
to other unknown Cochliodonts. 
Form. & Loc. Lower Carboniferous (Bone-bed in Lower Limestone 
tShales) : Avon Gorge, near Bristol, Gloucestershire. 
P. 2620. series of thirty teeth, comprising two much worn 
examples of the “ upper ” dental plate and imperfect 
specimens of the “lower;” the anterior teeth re.semblc 
those figured by Agassiz, and many are of remarkably 
large size, if timly referable to this species. There appears 
to bo a third form of dental plate, closely resembling the 
“ lower ” in shape, but more convex. Ennwlnlkn Coll. 
P. 2645. Tooth approaching the form of the so-called Uehdus 
mciminiltaris. Enniskillen Coll. 
P. 1434 a. Two “ upper ” dental plates, one shown of the natural 
size in PI. VI. fig. 16. Eyerton Coll. 
P. 1434. Twenty-foUr anterior teeth, and one imperfect small 
dental plate, apparently like the “ lower,” but more 
convex. Home of the elongated teeth exhibit wide trans- 
