358 BRACHIOPODA: ANOMIADZ. 
General Observations on this Class. 
The animals of this Class, like the Ginglymaconcha, have a 
bilobate mantle, and this mantle is always open; but their 
branchiee, which are also bilobate (as in most of the families of 
Ginglymaconcha), are bordered with small foliations or leaves 
on each lobe interiorly : in leu of the foot in the Ginglyma- 
concha, they have two fleshy arms, covered with numerous 
filaments, which are withdrawn when the valves are closed. 
They have two aortic hearts, and a flexuous intestinal canal, 
which runs round the liver ; the mouth is situated between the 
bases of the arms; the anus is situated on one of their sides. 
But little is known respecting the circulation, or the nervous 
system. 
This Class contains but three genera, Lingula and Terebra- 
tula of Bruguitre; and the Criopus, Poli; Crania, Lamarck ; 
Orbicula, Cuvier: the two last only are natives of Great 
Britain. 
Genus 1. Criopus. 
Criopus, Poli. 
Crania, De Lamarck. 
Orbicula, Cuvier, Blainville. 
Shell inequivalve, suborbicular; the right valve flat and 
fixed beneath ; its interior surface is perforated with three un- 
equal oblique openings ; the left valve is convex and rather 
gibbous, and internally is furnished with two protuberances. 
Criopus ORCADENSIS. 
The shells with their right valve conic, smooth, with the 
epidermis orange, painted with red circles; their left valve 
flattened, with the epidermis iridescent, variegated with purplish 
pink and fulvous, internally purplish, with its margin greenish. 
Length six lines ; height five and three-quarter lines. 
This extremely rare species was taken in the Orkneys in very 
deep water by Mr. W. Bullock, together with two specimens 
of Terebratula striata, adhering to the same stone. 
