8 
BRACHIOPODA. 
Order I. Ancylobrachia. 
The oral arms are attached to two shelly plates arising from 
the hinder or cardinal edge of the ventral valves ; they are re- 
curved and convolute on the inner side of the lamina. The animals 
are generally attached to marine bodies by a tendinous peduncle, 
which passes through a hole in the top of the umbo of the larger 
or dorsal valve ; this peduncle and the hole are sometimes obli- 
terated in the older specimens. 
The order only contains a single family, 
Fam. 1 . Terehratulidw, 
which is nearly synonymous with the smooth Terebratula of 
Sowerby, the perforated Terebratula of Carpenter, the genus 
Epithyris of Philhps and Terebratula of King, the family Tere- 
bratulida of M‘Coy, and Cyclothyridce of Phillips. 
The animal has been described by Linnaeus, Pallas, Ow'en, 
Blainville, Philippi, D’Orhigny and others. In some genera the 
hoops are united together below by a transverse band which is 
attached to medial longitudinal ridges of the ventral valve, as in 
Terebratula of Retzius = the Terebratella of D’Orbigny, as T. 
dorsata and Magas, Sow. In others the hoop forms a ring, and 
is free from the ventral valve, as Gryphus, Megerle^ Terebratula, 
D’Orb. and Terebratulina, D’Orbigny, for T. vitrea and T. caput 
serpentis. D’Orbigny indicates other genera under the names of 
Terebrirostra and Fissirostra. 
Order II. The Cryptobrachia 
have the oral arms entirely attached in the form of two or more 
lobed processes sunk into the grooves in the disc of the ventral 
valve. They are generally thick shells. This order also con- 
sists of only a single family. 
Fam. 1. Thecideadee. 
The animals are described by Phihppi and D’Orhigny. The 
genus Argiope, De Longchamps = Megathiris, D’Orb. {Tereb. 
detruncata) is attached by a tendon passing out of a very large 
perforation below the beak of the dorsal valves : Philippi con- 
founds this genus with his Orthis, which is different from the 
Orthis of Dalman. Thecidcea has the shell attached by the trun- 
cated apex of the dorsal valve, or it is free w'hen the apex is pro- 
duced and entire. De Longchamps, who estahhshed the genus 
Argiope in 1839, pointed out the affinity of this genus to The- 
cidcea. 
Subclass 2. Helictopoda. 
The oral arms are elongate, regularly spirally twisted when in 
repose. The mantle-lobes are merely appfied to the inner surface 
