14 
PALAEONTOLOGY OF NEW YORK. 
On the basis of the above mentioned peculiarity, 
Mr. Dall has separated such forms as L. albida from the 
genus Lingula, under the generic term Glottidia * i. e., 
shells in which the pedicle-valve bears two diverging 
parietal ridges and the brachial valve a median ridge 
of about the same length. Representatives of Mr. 
Dall’s genus have been regarded as confined to liv¬ 
ing species,^- and as representing the genus Lingula in 
American seas. 
Glottidia Palmeri, after Davidson. 
Fig. 10. Pedicle-valve. 
Fig. 11. Brachial valve. 
The name Dignomia was proposed in 1871 for certain Devonian and Silurian 
species, which are characterized by a strong longitudinal septum in “one or 
both valves.”^; 
Type, Lingula alveata, Hall, of the Hamilton shales. 
In this species, the median septum is sometimes strong and sharp, sometimes 
broad and low, with raised margins precisely as in the pedicle-valve of L. 
anatina (see figures of the species, Plate I). In addition, however, to the 
median septum, L. alveata , the type species, shows distinct evidence of diverg¬ 
ing parietal ridges, and, moreover, is the only American fossil species that is 
known to retain these as a persistent feature. The presence of the longitudinal 
septum alone in some degree of development, is by no means a rare 
feature among the palaeozoic species, and, as before observed, specimens fre¬ 
quently give evidence of the fact that this has been partially or wholly formed 
by progressive accretions to the anterior or median muscular fulcra. (See 
further on this point the observations on the formation of the platform in the 
Trimerellids.) Thus it has attained different degrees of development in 
L. quadrata of the Trenton, L. Iowensis of the Galena limestone, L. 
* American Journal of Conchology, vol. vi, p. 157, pi. viii, figs. 1-6. 1S70. 
f Mr. IIavidson calls attention to the close similarity apparent in Glottidia Palmeri, Dali, and Lingula? 
Lesueuri, Rouault, in respect to these septal ridges. (BrachiopodaoftlieBudleigh-Salterton Pebble-bed, p. 
362.) We have just referred to Prof. King’s suggestion that the latter species should be placed in a 
distinct genus, on account of its strong deltidial callosities, apparently adapted for the articulation of the 
valves,'and it will probably prove a representative of the genus Barroisella (q. v.). 
I Halo, On some Imperfectly known Forms among the Brachiopoda. 1871. 
