i4 
ERIK A : SON STENSIO 
height is situated only slightly caudally of the high and weakly convex anterior 
margin. From this the upper and lower margins converge fairly strongly backwards 
and meet in a fairly prominent, but still somewhat rounded angle. The shape of the 
scales can therefore be conveniently compared to an isosceles triangle, with its angles 
rounded off and its base directed forward. On most of the scales there is strong 
sculpture consisting of sharp striae, mostly fairly long and situated close together; the 
striae may sometimes run horizontally and fairly parallel to each other, sometimes, on 
the other hand, they converge backwards. They are never quite straight, however, but 
are more less undulating, nor are they situated in a line one after the other, but 
alternate in a fairly irregular way. The middle ones are not infrequently somewhat 
stronger than those situated dorsally and ventrally of them, being about as strong as in 
Axelia. The exposed part of the lateral surface of the scales 
is rather considerable compared with the size of the scales. 
* * 
Geological occurrence und localities. — Scler- 
acanthus asper occurs in the fish horizon, where it is rather 
rare. It has been found at Mt Congress, Mt Milne Ed¬ 
wards and Mt Andersson. 
Mylacanthus? or Scleracanthus ? sp. 
(Pi. 18, fig. 3). 
Under this heading I place provisionally a part of a 
cranial roof (P. ig8) that originates from a rather large 
Coelacanthid. This part comprises the fronto-dermosphenotic 
and a number of the dermal plates on the dorsal side of 
the ethmoidal region. 
As far as can be judged from the specimen present, 
the head has been strikingly broad and short, at least in 
its orbitotemporal and ethmoidal regions (text fig. 51). 
The fronto-dermosphenotics (Fr. dsph, text fig. 51; PI. 18, 
fig. 3 ) were short and broad. The postrostrals are divided 
into two independent bone-plates, a smaller anterior one (Ptr lt text fig. 51; Pl. 18, fig. 3 ), 
triangular in shape, and a considerably larger posterior one (Ptr 3 , text fig. 51; PI. 18, 
fig. 3 ), pentagonal, which is attached to the posterior plate of the opposite side by a 
short median suture. The interrostral (Ir) is, as far as can be seen, paired and is almost 
quite wedged in by the anterior and posterior postrostral plate on each side. The two 
interrostrals meet in the median line in a straight suture and are attached anteriorly 
for a short distance to the rostrals (R, text fig. 51). The latter are four-sided, arranged 
bilaterally symmetrically, and were probably represented by four plates on each side 
of the median line. Of these the most lateral one, which has been situated antero-laterally 
of the nasalo-antorbital, is the next largest one. The largest one is situated nearest to the 
median line. The latter one is attached posteriorly partly to the interrostral, partly to 
the anterior postrostral plate; the two rostral plates situated between the lateral and 
Mylacanthus or Scleracanthus? sp. 
The anterior part of the cranial roof. 
From P. ig8. V*. 
Fr. dsph, fronto-dermosphenotic; Jr, 
interrostral; Pa.it, parieto-intertempo- 
ral; Ptr v anterior postrostral plate; 
Ptr 2 , posterior postrostral plate; li. 
