30 
PALAEONTOLOGY OF NEW YORK. 
in the adjacent beds, and the more recent discovery by Dr. Warth, of trilobites 
in the “ Obolus-beds,” which have been referred by Waagen to the genera 
Conncephalites and Olenus{?), point conclusively to such an age.* Never¬ 
theless, some of the brachiopod genera show certain details of structure which 
indicate an important progress from the types exemplified in their nearest 
primordial allies; for example, the great cardinal process in Neobolus, the 
hinge-line in Cardinocrania, and thus, also, in Lakhmina, the cardinal process 
in the brachial valve is developed to a greater degree than has been observed 
among the later Trimerellids. The peculiar modification of the platform in this 
valve is also an important character. The advance apparent in the develop¬ 
ment of this feature in the brachial valve of Lingulops and Lingulasma, over 
that of the opposite valve, is here seen in the strongly elevated, though short, 
deeply enrolled posterior plate. The single species of this genus is quite small, 
and some of its internal characters are not well understood. 
The genera Trimerella, Dinobolus, Monomerella, and Rhinobolus, show a 
remarkable uniformity in their broadest characters, which may be expressed 
by the following analysis of the Family Trimerellidjs, Davidson and King: 
Shells essentially calcareous, usually thick and heavy. Umbo of the pedicle- 
valve generally high, solid or hollow; when the latter, double or triple- 
chambered. Cardinal area well developed; hinge-line inarticulate or with 
rudimentary teeth (?) ; supported in the pedicle-valve by a vertical axial 
wall or buttress. Each valve bears, in its -post-median portion, a more or 
less conspicuously developed platform, which may be solid or hollow; when 
the latter, it is double-chambered; from its anterior end extends a vertical 
septum, which is usually larger in the brachial, than in the pedicle-valve. A 
narrow crescentic impression lies just within the hinge-line, terminating 
within the lateral margins in broad muscular scars. The surface of the plat¬ 
form bears three or four pairs of similar scars. The pallial sinuses make a 
broad curve over the anterior area of each valve. 
This group has been made the subject of an exhaustive analysis by Drs. 
* See Note on the Discovery of Trilobites by Dr. H. Warth, in the Neobolus-beds of the Salt-Range ; 
by the Director, Geological Survey of India: Records Geol. Surv. India, vol. xxii, pt. 3, p. 153. 1889. 
