181 
COCHLIODOXTllLE. 
Psephodus laevissimus (Agassiz). 
1838. Heloclus Icevissimus, L. Agassiz, Poiss. Foss. vol. iii. p. 104, pl.xiv. 
figs. 1-14 ( non fig. 15). 
Type. Detached teeth and dental plates ; Bristol Aluseum (in 
part). 
A small species, the “ upper ” dental plate measuring about 
0013 autero-posteriorly. Inner margin of “upper” plate nearly 
straight anteriorly for more than half its length, then sharply 
bent upwards .almost at right angles and equally straight; coronal 
contour raised into a prominent narrow ridge along a line connecting 
the bend of the inner border with the posterior extremity of the 
outer border. “ Lower ” dental plate gently and more uniformly 
rounded than the “ upper inner margin very slightly curved. 
The “ upper ” dental plate is shown by Agassiz, Joe. cit. fig. 13, 
but the specimen is 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 Tomodus, and caunot be associated 
with P. Icevissimus upon present evidence. It is also uncertain 
whether many of the so-called anterior teeth of this species are 
correctly so determined, some being very large and perhaps belonging 
to other unknown Cocliliodonts. 
Form. <$c Loc. Lower Carboniferous (Bone-bed in Lower Limestone 
Shales) : Avon Gorge, near Bristol, Gloucestershire. 
P. 2820. A series of thirty teeth, comprising two much worn 
examples of the “ upper ” dental plate and imperfect 
specimens of the “ lower the anterior teeth resemble 
those figured by Agassiz, and many are of remarkably 
large size, if truly referable to this species. There appears 
to be a third form of dental plate, closely resembling the 
“ lower ” in shape, but more convex. Enniskillen Coll. 
P. 2845. Tooth approaching the form of the so-called Helodus 
mammillaris. Enniskillen Coll. 
P. 1434 a. Two “ upper ” dental plates, one shown of the natural 
size in PI. YI. fig. 16. Egerton Coll. 
P. 1434. Twenty-four anterior teeth, and one imperfect small 
dental plate, apparently like the “ lower,” but more 
convex. Some of the elongated teeth exhibit wide trans- 
