BRACHIOPODA. 
209 
and is triangularly cut open in the middle up to the very apex of the valve, 
which also is a little cut out. There is no cardinal process. On both sides of 
Fig. I5e. Fig. 157. 
Tereljratuloidea Davidsoni, Waagen.; 
Fig. 156. View of the exterior. 
Fig. 157. Interior of the pedicle-valve. 
Fig. 158. Interior of the bi'achial valve. 
Fig. 153. 
(Waagen.) 
the median incision very short curved crura take their origin, and proceed for 
a short distance in a slightly diverging direction towards the interior of the 
shell. There is no median dorsal septum. 
“ The muscular and vascular impressions are not sufficiently distinct to be 
described accurately.” (Waagen, op. cit, p. 414.) 
Type, Terebratuloidea Davidsoni, Waagen. Permo-Carboniferous. 
Observations. The difference existing between these shells and those con¬ 
stituting the subgenus Pugnax, appears to be mainly in the constant presence, 
in all later growth-stages, of a large apical truncating foramen. Dr. Waagen 
makes this a feature of first importance. Its character at maturity and its 
presence in immature phases of the shell are a repetition of the facts observed 
in Cyclorhina nohilis; like the latter, also, the exterior of the shell suggests a 
spire-bearing interior, and Waagen mentions his surprise at the discovery that 
his shells were rhynchonelloid. But for the presence of this highly developed 
foramen it would be difficult to distinguish the Indian shells from some of the 
small species of the American Upper Carboniferous faunas, belonging to the 
subgenus Pugnax, which have the foramen normally concealed at maturity and 
but partially enclosed at any stage of growth. In the former it is fully devel¬ 
oped at an early stage and maintained throughout the subsequent history of the 
individual. The relation of Terebratuloidea to Pugnax thus appears to be 
that of a senile to an immature condition of development. 
