328 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britain. 
own and the late Mr. Wood’s collections, to the York Museum, has set an example 
worthy of emulation), Mr. William Horne, of Leyburn, in Wensleydale, to whose 
rich private collection I have had free access. To Mr. Walter Keeping, at the 
Woodwardian Museum, and his son, Mr. W. Keeping, at York, [ am obliged for 
kindly rendered attentions, and to Mr. W. Percy Sladen, my dear friend and near 
neighbour, for help not easily expressed in words—to many others my thanks are 
due and heartily tendered. 
To Lord Enniskillen, without whose aid this memoir would have been well nigh 
impossible, I cannot sufficiently express my sense of obligation. His great and 
practical knowledge of the fossils in his collection ; his intimate intercourse with 
that learned ichthyologist, the author of “ Poissons Fossiles,” and the knowledge 
his lordship possessed of the unpublished researches of M. Agassiz, have, in some 
departments, rendered my labour comparatively easy, whilst the genial and kindly 
friendship always exhibited has rendered my work at all times most agreeable. 
2, CLAssrrieD Description oF THE FossiL FISHES. 
PIScEs. 
4 is proposed in the following descriptions to adopt the classification recently 
(1880) published by Dr. Albert C. L. G. Giinther in his “ Introductory Study of 
Fishes.” The class Prsczs is divided into four sub-classes, viz.:— 
J. Paleeichthytes. 
II. Teleostei a Teleostei (Huxley). 
Ill. Cyclostomata — Marsipobranchii (Huxley). 
IV. Leptocardu = Pharyngobranchii (Huxley). 
The fishes of the Mountain Limestone formations belong exclusively to the 
first sub-class which is defined as follows by Dr. Giinther. 
I. PALAICHTHYTES. 
Heart with a contractile conus arteriosus ; intestine with a spiral valve ; optic 
nerves non-decussating, or only partially decussating ; skeleton cartilaginous or osseous. 
This sub-class is divided into two orders, viz.:—the Chondropterygu and the 
Ganoidei. The former being equivalent to the Hlasmobranchiw (Bonaparte) of 
Professor Huxley’s classification, and including the sharks, rays, and chimeras. 
The latter embraces the orders Ganoidet and Dipnoi of Professor Huxley. 
Order 1. CHONDROPTERYGII. 
“Skeleton cartilaginous. Body with median and paired fins, the under pair 
