BRACHIOPODA. 



209 



and ii< 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. IX. Hij. la'. 



Terebratuloidea Davidsoni, \Vaagen.| 

 Fig. 15G. View of tiie exterior. 

 Fig. 157. Interior of the pedicle-valve. 

 Fig:. 158. Interior of tiie braciiial valve. 



FIG. 158. 



(VVaaOKX.) 



the median incision ver}^ 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. cii, 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 nobilis ; 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. 



