in the plural into
-es_:--

_Sing._ _Plur._ | _Sing._ _Plur._
Amanuens-is amanuens-es | Ellips-is ellips-es
Analys-is analys-es | Emphas-is emphas-es
Antithes-is antithes-es | Hypothes-is hypothes-es
Ax-is ax-es | Oas-is oas-es
Bas-is bas-es | Parenthes-is parenthes-es
Cris-is cris-es | Synthes-is synthes-es
Diaeres-is diaeres-es | Thes-is thes-es.

THIRD CLASS.

_Words wherein the plural is formed by inserting -e between the last two
sounds of the singular, so that the former number always contains a
syllable more than the latter:--_

_Sing._ _Plur._
Apex _sounded_ apec-s apices
Appendix -- appendic-s appendices
Calix -- calic-s calices
Cicatrix -- cicatric-s cicatrices
Helix -- helic-s helices
Index -- indec-s indices
Radix -- radic-s radices
Vertex -- vertec-s vertices
Vortex -- vortec-s vortices.

In all these words the c of the singular number is sounded as k; of the
plural, as s.

s. 82. The following is a list of the chief Greek substantives lately
introduced, and preserving the _Greek_ plural forms--

FIRST CLASS.

_Words where the singular termination -on is changed in the plural into
-a_:--

_Sing._ _Plur._ _Sing._ _Plur._
Apheli-on apheli-a Criteri-on criteri-a
Periheli-on periheli-a Ephemer-on ephemer-a
Automat-on automat-a Phaenomen-on phaenomen-a.

SECOND CLASS.

_Words where the plural is formed from the original root by adding either
-es or -a, but where the singular rejects the last letter of the original
root._

_Plurals in_ -es:--

_Original root._ _Plur._ _Sing._

Apsid- apsid-es apsis
Cantharid- cantharid-es cantharis
Chrysalid- chrysalid-es chrysalis
Ephemerid- ephemerid-es ephemeris
Tripod- tripod-es tripos.

_Plurals in_ -a:--

_Original root._ _Plur._ _Sing._

Dogmat- dogmat-a