BRACHIOPODA. 
63 
its anterior extremity. Just behind its termination is a pair of small, usually 
indistinct muscular impressions, probably the scars of the central muscles. 
In the brachial valve the beak is scarcely prominent, and the muscular mark¬ 
ings are essentially as in the opposite valve, but more sharply developed. 
Beneath the beak is a faint umbonal scar, the diverging lines from which are 
discernible. The long, compound lateral curves have a considerably greater 
degree of curvature than in the pedicle-valve, their posterior portion enclosing 
a thickened area, which is continued into a peculiar low and thickened median 
septum, bifurcating in the middle of the valve, the angle being occupied by 
an intercalated ridge, which extends for twice the length of the branches of 
the septum. This peculiar bifurcation may be due to the impression of the 
anterior muscular scars at this point. The central scars are situated further back¬ 
ward at the junction of the median septum with the posterior thickened area. 
Type, Lingula subspatulata, Meek and Worthen. 
Observations. There can be no sufficient reason to doubt the generic differ¬ 
ence of shells possessing the above characters from described linguloids. The 
condyles on the cardinal margin are themselves a dis¬ 
tinctive feature. We have already directed attention 
to Dr. King’s observations upon this peculiarity in 
Lingula ? Lesue.uri, Rouault,* _ a species which shows 
evidences upon the cast, of two deep pits close to the 
beak. In his opinion this character alone is sufficient 
to exclude the species from the genus Lingula. Mr. 
Davidson subsequently comparedf this species ( L. Le- 
After Davidson. 
both the development of a median septum in the pedicle- 
valve and two lateral septa in the brachial valve. Just such septal features are 
found in the pedicle-valve of B. subspatulata if we choose to consider the diverg¬ 
ing umbonal furrows as homologous with the lateral septa in Glottidia ; but they 
are not found in the brachial valve. The other internal markings of this species 
are widely different from those of Lingula. The central muscular scars are 
* Vide supra. Armais and Magazine Natural History, July, 1873, p. 13. 
f Brachiopoda Budleigh-Salterton Pebble-bed, p. 362. 
