BRACHIOPODA. 
213 
short, while the supporting septum is carried beyond it, sometimes to nearly 
one-half the length of the shell. Near the teeth, which are small, there are 
two accessory supporting lamellae abutting on one side against the outer surface 
of the converging dental plates, and on the other against the interior cardinal 
surface of the valve ; thus enclosing small lateral umbonal cavities. Muscular 
scars of this valve always obscure. 
In the brachial valve the cardinal plate is narrow, subtriangular, in the 
typical species bearing a very small cardinal process, which in other species is 
rarely present. The hinge-plate is traversed by two fine, divergent ridges 
running outward from the beak and continuous beyond the anterior edge of 
the plate into long, slender and upwardly curving crura. Beneath the crura 
arises a broad, shallow, trough-shaped plate, which, near the apex, is supported 
by a short median septum resting on the valve. This process is strongly curved 
toward the opposite valve and is continued for most of its length beyond 
the termination of the median septum. Usually it widens outwardly, and then 
narrows rather abruptly, or even acutely, to its extremity. The adductor 
muscular scars are well developed in this valve, forming a broadly oval or sub- 
circular impression. 
Vascular sinuses are sometimes retained on both valves. 
Type, TerebratuHtes Schlotheimi, von Buch."^ Permian. 
Observations. According to our present knowledge, this genus represents the 
latest appearance of the camarellid interior. Its relations to the various groups 
of the rhynchonellids is largely, and we may say with a single reservation, 
wholly external. Species of Camarotoichia do develop, in the brachial valve, 
an elongate cavity on the summit of the median septum ; this is always in an in¬ 
cipient condition and is attained quite independently of any association with, or 
derivation from Conchidium and its allies. From this source may have come the 
brachial spondylium of Camarophoria, though the mode of attachment beneath, 
instead of in continuity with the hinge-plate, may perhaps render such assump- 
* Dayidson, at various times, expressed the opinion that this specific term should be regarded as a syn¬ 
onym for Martin’s Conchyliolitlius anomites crumena, from the Carboniferous limestone. There are some 
differences in the two shells as described and illustrated by Mr. Davidson, and as the typical forms of each 
are from distinct faunas it is wiser to keep them apart. The Permian shell is the type of Camarophoria. 
