APPENDIX. 245 
disposed to consider, that similarity of apophysary systems constitutes a stronger bond of generic affinity 
than similarity of external characters ; and in this respect, I believe, that I am fortified by the opinion of 
Mr. Davidson, whose knowledge of the interiors of Ancylobrachial genera is of the highest order. 
Now, as the first-described genus of the singly-attached-looped Ancylobrachial group is Terebratula, it * 
will be necessary, in considering this group as a family, to name it Terebratulide ; and, on the other hand, 
as the original genus of the doubly-attached-looped Ancylobrachials is Terebratella, we are also compelled 
to consider these, as constituting the family Terebratelide. These two families may, therefore, be con- 
stituted as follows: 
Terebratulide. Terebratellide. 
(Genera with a singly-attached loop.) (Genera with a doubly-attached loop.) 
Terebratula. Terebratella. 
Terebratulina. Megerlia. 
Delthyridea (°) Ismenia. 
Waldheimia. 
Epithyris. 
Pygope. 
It requires to be observed, that I now entertain very little opinion of any of the above genera being 
without an apophysary system : if this be correct, Rhynchora will have to be stationed in either one or 
the other of the above families. The family Rhynchoride, if its type have a doubly-attached loop, will have 
to bear this name instead of that of “ Terebratellide ;’’ but until this is settled, it seems preferable to make 
use of the latter name. 
Strophalosia Morrisiana, p. 99. 
An oversight was made when describing this species. Nothing was then stated of the lower or small 
valve being furnished with spines. Figure 26, in Plate xii, represents a gutta percha cast of an impression 
of this valve, found in Whitley Quarry, which shows that the spines are not so numerous as those of 
Strophalosia excavata, nor so regularly arranged. 
Spiriferide (Apophysary system of), p. 122. 
In noticing the cross-piece which Mr. Davidson has discovered connecting the two spirals of some of the 
Jurassic forms of this family, I made the suggestion, that it had resulted from the approximation or union of 
the two crural processes. This view is strongly supported by what is seen in the loop of Terebratulina 
caput-serpentis, as will be shown hereafter. 
Ismenia, pp. 142-145. 
Through an error, I typified this genus with Schlotheim’s Terebratulites pectunculus, instead of his 
Terebratulites pectunculoides. I am enabled, by the beautiful figure which Mr. Davidson has lately 
published of the latter species (Vide Annals and Mag. of Nat. Hist., 2d series, vol. v, plate xv, fig. 5), 
to add to the diagnosis of this genus the following character of its apophysary system: Loop elongated ; 
deeply recurved ; armed at the recurving bend with several cilia-like processes ; and attached anteriorly to a 
long medio-longitudinal plate. 
