532 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
the other by the prolongation of the ribs upon which they are fixed. The interior 
of the spine is hollow almost to the summit, and the walls are thin. The posterior 
margin is armed with small spines directed obliquely towards the base. 
This genus has frequently been associated in collections with (Gorcallen) 
Oracanthus, to which in some respects the specimen now to be described bears ‘a 
resemblance. Its walls are thin, with large internal cavity, the long slender form of 
this genus is, however, quite distinct from the triangular and irregular outline of 
Oracanthus and the tubercles instead of being arranged as in that genus, are placed 
in regular longitudinal rows. Prof, de Koninck suggests a resemblance to Physone- 
mus of M‘Coy, it appears to be a very superficial one in the present case. 
Stichacanthus tortworthensis, Davis. 
(PISHEXGVyahics 22) 
Spine, medium size, long and comparatively slender, gently arched, much 
compressed, imperfect, basal and apical terminations absent—-part preserved is 
eleven inches in leneth—greatest width near base 2°3 inches, gradually diminishing 
to °8 of an inch at the part nearest apex which is preserved. A transverse 
section is oval, laterally compressed or flattened, the anterior and posterior 
extremities of the section being more or less pointed. The surface is ornamented 
by a numerous series of longitudinal ridges, decreasing by inosculation as they 
approach the apex. The ridges extend parallel for the most part with the 
concave (posterior?) margin. The ridges are produced at short intervals so as 
to form nodular tubercles, broadly implanted, rounded and smooth at the top. 
The ridges are separated by longitudinal furrows, which are again subdivided by 
minute striations especially towards the basal extremity. The walls of the spine 
are thin, and the internal cavity large. The basal portion which may have been 
implanted in the body of the fish is not preserved. Along the convex margin of 
the spine the tubercles are larger than on the sides, and present the appearance of 
denticles : the tubercles on the concave margin do not present any special feature. 
This species differs from Stichacanthus cemansi, de Koninck, by its length being 
considerably greater in proportion to its diameter at the basal extremity ; in the 
smaller size of the dermal tubercles, the longitudinal ridges being narrower and 
more numerous; and in the subdivision of tae ridges by striz. 
I have ventured to designate this species by the nomen triviale derived from the 
locality where the specimens have been found, which was in the immediate vicinity 
of Tortworth Court, the seat of the Earl of Ducie, to whom I am indebted for the 
opportunity of describing the specimens included in this genus, and the great spine 
for which I have been obliged to establish the following genus. 
Formation and locality: Mountain Limestone, Tortworth. 
Ez coll. Earl of Ducie, Tortworth Court. 
