A CARBONIFEROUS BRACHIOPOD 657 



therefore the septa do not extend to the cardinal process as in some of 

 the Productidae. The scars of the adductor muscles lie on each side 

 of the mesial septum, extending over the next ridge. The brachial 

 markings, shown on a few specimens of this valve, are somewhat 

 obscure, and reniform in shape, pointed at the front. They lie on 

 each side of the mesial septum, just within the row of granules marking 

 the limits of the visceral cavity. 



This valve is ornamented with granules (from which the species 

 derives its name of granulijer) . These are largest and most numerous 

 at the forward edge of the visceral cavity, and the mesial sinus, 

 growing fainter and more thinly scattered posterially. At the anterior 

 margin they also grow fainter until they form distinct radiating rows. 



Interior of ventral valve. — Very concave. Granules similar to 

 those of dorsal valve, except that instead of having a group of granules 

 on the anterior end of the mesial septum, they are arranged along its 

 sides and help to form the partition between the long, median adduc- 

 tor muscle scars and the subovate diductor muscle scars. Hinge-line 

 straight, with the exception of the delthyrium. There are two teeth 

 on each side of this opening. The deltidium extends to the beak. 



Nepionic form — dorsal valve. — ^Length i mm and breadth i mm. 

 Longitudinally semi-elliptical in shape; concavity greater than in 

 mature form in proportion to the size. The convexity mentioned 

 as being opposite the beak near the hinge on the dorsal valve of the 

 mature form, is the most prominent feature of this valve of the incipient 

 form. Here it nearly equals the length of the shell and is more 

 elongate than in the adult. Surface without striae. 



Nepionic form — ventral valve. — This valve is also without striae. 

 On each extremity of the hinge-line is a spine pointed laterally and 

 posteriorly. The ventral mesial sinus is a regular feature of this 

 valve, A sharply outlined pit also occurs regularly on this valve 

 just anterior to the beak. 



DEVELOPMENTAL CHANGES 



The change in shape may be seen from the following table of 

 the measurements of a series of specimens (not the series shown in 

 Plate I). 



