VINE: CARBONIFEROUS POLTZOA. 
171 
of King's types is recorded, and a fresh description of T. duhius 
is given, after a careful comparison of the Permian specimens in the 
Newcastle Museum. 
The Derbyshire species is comparatively rare, but I have been 
sing-ularly fortunate in the fragments given to me by Mr. Aitken. 
I have both the reverse and the obverse, and besides this, there are 
several smaller fragments which afford good diagnostic characters. 
In founding the Genus Thanmiscus Prof. King says " It embraces 
the two following genera, one of \\\i\ch. ( Thamniscus) is the type, 
and apparently Mr. McCoy's Ichthyorachis. ( Permian Foss. p. 43.^ 
The foUo^ving is McCoy's description of this genus : — 
Genus Ichthyorachis, McCo3\ 
A straight central stem, having on each side a row of simple branches 
or pinnae, all in the same plane, obverse rounded, without keel, each 
hearing several rows of small prominent oval pores, arranged in 
quincunx, reverse smooth, or finely striated. (Carb. Foss.) 
The only species /. newenhmmi^ McCoy, County Clare, Ireland. 
The type of this genus appears to correspond more closely as an 
ally of Glauconortie than Thamniscus^ yet there are specimens amongst 
my Derbyshire collections that seem to reconcile the apparent conflict 
of opinions, but I do not think we shall be able to maintain McCoy's 
genus as a separate type. I will endeavour to describe fairly the 
two types and leave the reader to judge. 
10. ICHTHTOKACHIS, S.p. 
Zoarium in its earlier stages, a strong central stem with lateral 
pinnse. These do not strike off at right or acute angles like 
GlaiLconome but the pinnae bifurcate as free branches, rather dimin- 
utive at first, but towards the apex of the branches as bold and 
unfenestrated twigs. In the earUer stage the cells are arranged on 
the surface of the stem in three rows, on the pinnae in two rows, and 
on the terminal free branches in from two to three rows. 
In a small fragment of another, or the true Thamniscus type, 
casts of the main stem remain with a few lateral depressions. A 
small poriferous portion still remaining in one of the furrows, show 
that the arrangement of, and character of the cells are similar to tlie 
variety already described. In the absence of better material I must 
