BBACHIOPODA. 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 suhspatulata, Meek and Worthen. 



Observations. There can be no suflficient 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 ? Lesueuri, Rouault,* a sjDecies 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- 

 sueuri) with the recent Glottidia Palmeri, Dall, finding in *'''^"^- -t"'ff«to '£««"«« ».Eouauu. 



■^ Internal cast of pedicle-valve. 



both the development of a median septum in the pedicle- ^''"''' Davidson. 



valve and two lateral septa in the brachial valve. Just such septal features are 

 found in the pedicle-valve oi B. -suhspatulata if we choose to consider the diverg- 

 ing umbonal furroAvs 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. Annals and Magazine Natural History, July, 1873, p. 13. 

 t Brachiopoda Budleigli-Salterton Pebble-bed, p. 362. 



