468 WELLBURN : FISH FAUNA OF THE PENDLESIDE LIMEVrONKS. 
surface being divided into a number of wide rounded ridges, and 
the grooves cutting deeply into the posterior margin gives it a scalloped 
appearance. On the posterior flank the scales appear to have been 
smooth. The head bones are not well seen in any specimen, but 
what evidence there is shows that they were of the ordinary Acan- 
thodian type. The bones of the shoulder girdle were strongly 
developed, and are very similar in form to those of Parixius. 
Form and Loc: Pendleside Limestones, Pule Hill, near Marsden, 
Yorkshire. 
Marsdenius acuta sp. nov. 
Type : Portion of fish, author's col. 
There are several specimens of this fish in the author's cabinets. 
They show the same general characters as the last of the type species, 
but a much smaller fish is indicated ; the type specimen would point 
to a fish of about 7 cms. in length. The fish differs, however, 
from the last species in the character and ornamentation of its fin 
spines, and also the sculpture of its scales. The pectoral fin spines 
are more elongated and slender ; they gradually taper to a fine point, 
and have a groove and ridge running parallel to the anterior border. 
The other spines are similar to those of the last species, with the ex- 
ception that the ridges which sculpture the spines are relatively 
much finer and more numerous and run in a more irregular manner. 
The clavicular bones are very strongly developed, and one specimen 
in the author's collection is of great interest, as it shows the form 
and characters of the mandible, with its dentition. The mandible 
is very similar in its general characters to that of the fish Acantho- 
dopsis Wardi Egerton of the Coal Measures. The dentition consists 
of w^ell-marked, blunt, broad, low cones, confluent at their bases. 
The scales are very minute, and here and there a scale sculpture 
of very fine transverse striae may be made out by the aid of a powerful 
lens. 
The name "acuta" is given to the fish on account of the pointed 
character of its pectoral fin spines. 
Form and Loc: Pendleside Limestones, Pule Hill, near Marsden, 
Yorkshire. 
