THE DEVONIAN FOSSILS OF CANADA WEST. 139 
composed, from Terebratula, Atrypa, Spirifera, and other genera to 
which they had been previously referred. His original description 
was published in the ‘Synopsis of the Carboniferous Fossils of 
Ireland,” in 1844. From this work we shall make the following ex- 
tracts:— 
“The family Delthyride appears to be divided into the five following genera: 
1. Spirifera, Sow., composed of those longitudinally-ribbed species, in which 
the hinge-line is equal to, or exceeds the width of the shell, the cardinal area 
with parallel sides, the cardinal teeth of the ventral valve (now called the dor- 
sal valve) large, spirally rolled, and having a triangular foramen beneath the ° 
beak of the dorsal (ventral) valve. 2. Martinia, McCoy, or the smooth Spiri- 
fers, in which the hinge-line is less than the width of the shell, and the cardinal 
area triangular. 3. Athyris, MeCoy, in which there is no vestige of either fora- 
men, cardinal area, or hinge-line. This remarkable genus is frequently con- 
founded with those shells usually named Zerebratula, in the older rocks, but is 
distinguished by the large, spiral appendages, which are wanting in the other 
group. 4. Brachythyris, McCoy, in which we find the longitudinally-ribbed 
surface of Spirifera, united with the short hinge-line of Martunia. 5. Orthis, 
Dal., in which there are no spiral appendages, the hinge-line and striae frequently 
spinose (as in Leptena), and the cardinal area common to both valves, and its 
Sides inclined towards each other at its angles; dorsal valve smallest.”—Work 
cited, page 128. 
On page 146 of the same work, he thus concisely deseribes the 
genus :-— 
“ Gen. Ch.—Nearly orbicular, small; no cardinal area or hinge-line; spiral 
appendages very large, filling the greater part of the shell. 
“This very interesting group possesses all the external characters of the 
Terebratulide, united to the internal strueture of the Spirifers, to which latter 
family it truly belongs. Professor Phillips is the only author who has recog~ 
nized the group: he forms of it his last division of the genus Spirifera, but gives 
no charaétters to distinguish it from Terebratula; the internal structure is, how- 
ever, a sure guide.” 
The above descriptions include all the more comprehensive and 
important characters, or those which connect the species together into 
one group by general affinities pervading the whole. In this respect 
nothing more has been done for this genus since 1844, although 
several minor and highly interesting points of the mternal arrange- 
ments, such as the complicated structure of the spires and the form 
of the muscular impressions, have been ascertained by other authors ; 
(especially by Messrs. Davidson, Bouchard, and Suess.) 
McCoy was under the impression that all of the species were desti- 
