BRACHIOPODA. 879 
directed towards the centre of the valve; teeth and impressions 
like Rhynchonella. 
The shells of this genus differ from Rhynchonella chiefly in 
the calcification of the oral supports, a character of uncertain 
value. 
Fossil, 21 species. Lower Silurian—Trias. America (Wel- 
lington Channel! Falkland Islands), Europe, Thibet. 
Anoplotheca lamellosa, F'. Sandberger, 1856, Devonian, Rhine, 
is a species of Atrypa. 
Famity [VY.—ORTHIDA.* 
Shel? transversely oblong, depressed, rarely foraminated ; 
hinge-line wide and straight; beaks inconspicuous; valves 
plano-conyex, or concayo-conyex, each with a hinge-area (/) 
notched in the centre ; ventral valve with prominent teeth (¢); 
muscular impressions occupying a saucer-shaped cavity with a 
raised margin; adductor (a) central; cardinal and pedicle 
impressions (r) conjoined, lateral, fan-like; dorsal yalve with a 
tooth-like cardinal process between two curved brachial pro- 
cesses (c); adductor impression (a) quadruple ; vascular impres- 
sions consisting of six principal trunks in the dorsal valve, two 
in the yentral, the external branches turned outwards and back- 
wards inclosing wide oyarian spaces (0). Indications have been 
E Wi, YY] ii} \ 
| Mi Ih i\\ i 
z ft fi ‘\\ Yi | 
ZA a3 My, |i 
SS : | KG Wy Wy" , 
Bre / i ins \ \\ 
Dorsal valve.f Ventral valve. 
Fig. 182. Orthis striatula. Devonian, Eifel. 
observed, in several genera, of horizontally-coiled spiral arms; 
the space between the valves is often very small. The shell- 
structure is punctate, except in a few instances, where the 
original texture is probably obliterated. 
* The names of the families are formed from those of the typical genera, by sub 
stituting zde for the last syllable of the genitive case. 
+ From a specimen presented by M. De Koninck to the British Museum; internal 
casts of this fossil were called hysterolites by old authors. 
