234 ON SOME FISH REMAINS FROM DURHAM 
ORDER. GANOIDEI. 
FAMILY. GLYPTODIPTERINI. 
GENUS. RHIZODUS, Owen. 
1. Ratzopus Ltancirormis, Newberry. PI. VL., Figs:-1, 2,08: 
Several teeth and a portion of one ramus of the mandible of 
this species have occurred to us. 
The teeth, by which the species is best known, are from 
Sths. of an inch to an inch in length; from 2ths. to +%ths. in 
width; and about ;,th. in thickness medianly. They are lancet 
shaped, acutely pointed, and with sharp, cutting edges; one 
edge is more convex than the other, and that which is least 
convex is most trenchant; the median portion is swollen or flatly 
convex; the lateral portions are slightly concave; the base 
appears to have been finely plicated; the rest of the surface is 
smooth; the cross section elliptical. 
The fragment of the mandibular bone is about 3 inches long, 
and 13 inch broad. Portions of two (?) teeth are shown in the 
interior, but both seem to be displaced. The external surface 
is sculptured in a bold, rugose sort of pattern, the ridges of the 
wrinkling being comparatively narrow and sharp, and the inter- 
vening furrows wide and shallow. 
Localities —Newsham and West Cramlington. It occurs 
also in the Coal Measures of North Staffordshire, Nova Scotia, 
and Ohio. 
GENUS. HOLOPTYCHIUS, Agassiz. 
2. HoLoprycuius sAUROIDES, Agassiz. Pl. VI., Figs. 5 & 6. 
The teeth of this species are usually found detached, but we 
have one specimen showing four of them fixed to a portion of 
the right ramus of the mandible. This fragment which shows 
the extremity, is 2? inches long, }2ths. of an inch high, and 
jgths. thick. Its external surface is irregularly swollen and 
densely covered with minute and somewhat irregular tubercles. 
A large laniary tooth, about 1 inch long, is placed on a pro- 
tuberance near its extremity, with a smaller one, ,7,ths. long, 
before it, and two others, }2ths. in length, placed together 
about 13 inches behind it. The space between the latter and 

