WELLBURN : FISH FAUXA OF THE PEXDLESIDE LIMESTONES. 467 
Marsdenius sUxMMITI, sp. nov. 
Type : Imperfect fish, author's col. 
The best specimen (the type) is in a Hmestone nodule. It shows 
a fish of about 10 cms. in length ; the caudal and ventral regions are 
"vvell shown, but the head being crushed back on to the dorsal region 
this portion of the fish is not so well shown. The body is fusiform 
and laterally compressed. Of the fins, the caudal is strongly developed, 
the lobes being prominent and well marked ; the pectoral ventral, 
and anal fins are fairly well seen and appear to have been well 
developed. The dorsal fins are not seen here, but another specimen 
which show^s their fin spines points to the fact that the posterior 
fin was the larger of the two. All the fins are covered with scales 
similar to those on the body, but smaller, and, with the exception of 
the caudal, all are provided with spines. In position the anal fin 
is close to the caudal, the ventral being about one-third nearer the 
pectoral than the anal. The pectoral fin spine is the largest and 
most elongated ; the ventral spine is about half the length of the 
pectoral : the anal rather smaller than the ventral ; the posterior 
dorsal about the size of the ventral : whilst the anterior dorsal spine 
is only about half the size of the posterior. On the ventral surface 
of the fish are several very small recurved free spines. The pectoral 
spine appears to have been smooth, with the exception of a single 
groove which runs parallel with Its anterior border. The spine 
is slightly curved ; the remainder of the spines are straight, robust, 
and ornamented with well-marked longitudinal ridges, which have 
the following arrangement : — The anterior one or two are more 
strongly marked than the others, and run parallel to the anterior 
border, whilst the more posterior ridges run longitudinally in a 
somewhat irregular manner, gradually converging towards the 
more strongly marked anterior ones. The body is covered with 
scales, which are very minute, and the superficial ornamental layer 
having been most removed, the scales mostly appear smooth, but 
here and there the sculpture can be seen by the aid of a powerful 
lens. It is as follows : — On the principal flank the scales are sculptured 
with deep grooves which traverse the scale in an anterior-posterior 
direction, parallel with the superior and inferior borders, the scale 
