emata (Beecher).--Inarticulate Brachiopoda, with the
pedicle passing out between the umbones, the opening being shared by
both valves. Pro-deltidium attached to dorsal valves.
FAMILIES.--PATERINIDAE, OBOLIDAE, TRIMERELLIDAE, LINGULELLIDAE,
_LINGULIDAE_, LIGULASMATIDAE.

ORDER II. Neotremata (Beecher).--More or less circular, cone-shaped,
inarticulate Brachiopoda. The pedicle passes out at right angles to
the plane of junction of the valves of the shell; the opening is
confined to the ventral valve, and may take the form of a slit, or may
be closed by the development of a special plate called the listrium,
or by a pseudo-deltidium. Pro-deltidium attached to ventral valve.
FAMILIES.--ACROTRETIDAE, SIPHONOTRETIDAE, TREMATIDAE, _DISCINIDAE_,
_CRANIIDAE_.

Class II. TESTICARDINES (ARTICULATA)

ORDER III. Protremata (Beecher).--Articulate Brachiopoda, with
pedicle-opening restricted to ventral valve, and either open at the
hinge line or more or less completely closed by a pseudo-deltidium,
which may disappear in adult. The pro-deltidium originating on the
dorsal surface later becomes anchylosed with the ventral valve.
FAMILIES.--KUTORGINIDAE, EICHWALDIIDAE, BILLINGSELLIDAE,
STROPHOMENIDAE, _THECIDIIDAE_, PRODUCTIDAE, RICHTHOFENIDAE, ORTHIDAE,
CLITAMBONITIDAE, SYNTROPHIIDAE, PORAMBONITIDAE, PENTAMERIDAE.

ORDER IV. Telotremata (Beecher).--Articulate Brachiopoda, with the
pedicle-opening, confined in later life to the ventral valve, and
placed at the umbo or beneath it. Deltidium present, but no
pro-deltidium. Lophophore supported by calcareous loops, &c.
FAMILIES.--PROTORHYNCHIDAE, _RHYNCHONELLIDAE_, CENTRONELLIDAE,
_TEREBRATULIDAE_, STRINGOCEPHALIDAE, MEGALANTERIDAE,
_TEREBRATELLIDAE_, ATRYPIDAE, SPIRIFERIDAE, ATHYRIDAE.

_Affinities_.--Little light has been thrown on the affinities of the
Brachiopoda by recent research, though speculation has not been
wanting. Brachiopods have been at various times placed with the
Mollusca, the Chaetopoda, the Chaetognatha, the Phoronidea, the
Polyzoa, the Hemichordata, and the Urochordata. None of these
alliances has borne close scrutiny. The suggestion to place
Brachiopods with the Polyzoa, _Phoronis, Rhabdopleura_ and
_Cephalodiscus_, in the Phylum Podaxonia made in _Ency. Brit._ (vol.
xix, ninth edition, pp. 440-441) has not met with acceptance, and
until we have a fuller account of the embryology of some