Pectinate

(Lat. pecten, a comb). Comb-like; applied to the gills of certain Gasteropods, hence called Pectinibranchiata.

Pectoral

(Lat. pectus, chest). Connected with, or placed upon, the chest.

Perennibranchiata

(Lat. perennis, perpetual; Gr. bragchia, gill). Applied to those Amphibia in which the gills are permanently retained throughout life.

Pedal

(Lat. pes, the foot). Connected with the foot of the Mollusca.

Pedicellariae

(Lat. pedicellus, a louse). Certain singular appendages found in many Echinoderms, attached to the surface of the body, and resembling a little beak or forceps supported on a stalk.

Pedicle

(Lat. dim. of pes, the foot). A little stem.

Pedipalpi

(Lat. pes, foot; and palpo, I feel). An order of Arachnida comprising the Scorpions, etc.

Peduncle

(Lat. pedunculus, a stem or stalk). In a restricted sense applied to the muscular process by which certain Brachiopods are attached, and to the stem which bears the body (capitulum) in Barnacles.

Pedunculate

Possessing a peduncle.

Pelagic

(Gr. pelagos, sea). Inhabiting the open ocean.

Pelectpoda

(Gr. pelekus, an axe; podes, feet). A name often applied to the Lamellibranchiata, on account of many of them having a hatchet-shaped or sickle-shaped foot.

Pelvis

(Lat. for basin). Applied, from analogy, to the basal portion of the cup (calyx) of Crinoids. The bony arch with which the hind-limbs are connected in Vertebrates.

Pergamentaceous

(Lat. pergamena, parchment). Of the texture of parchment.

Pericardium

(Gr. peri, around; kardia, heart). The serous membrane in which the heart is contained.

Periderm

(Gr. peri, around; and derma, skin). The hard cuticular layer which is developed by the coenosarc of certain of the Hydrozoa.

Perigastric

(Gr. peri, around; and gaster, stomach). The perigastric space is the cavity which surrounds the stomach and other viscera, corresponding to the abdominal cavity of the higher animals.

Periostracum

(Gr. peri; and ostrakon, shell). The layer of epidermis which covers the shell in most of the Mollusca.

Periplast

(Gr. peri; and plasso, I mould). The intercellular substance or matrix in which the organised structures of a tissue are embedded.

Perisarc

(Gr. peri, around; sarx, flesh). Employed by Prof. Allman as a general term for the chitinous envelope secreted by many of the Hydrozoa.

Perisome

(Gr. peri ; and soma, body). The coriaceous or calcareous integument of the Echinodermata.

Perissodactyla

(Gr. perissos, uneven ; daktulos, finger). Applied to those Hoofed Quadrupeds (Ungulata) in which the feet have an uneven number of toes.

Peristome

(Gr. peri; and stoma, mouth). The space which intervenes between the mouth and the margin of the calyx in Vorticella ; also the space between the mouth and the tentacles in a sea-anemone (Actinia); also the lip or margin of the mouth of a univalve shell.