rostrum

(1) Anteriorly projecting, unpaired, usually rigid median extension of carapace between eyes or ocular peduncles; (2) anterior beaklike projection of valve margins overhanging incisure or notch (Ostracoda); (3) unpaired anteroventral plate of thoracic Cirripedia; in lepadomorphs, 1 of up to 4 unpaired plates of capitulum; in verrucomorphs, compartmental plate between carina and fixed scutum; in balanomorphs, compartmental plate overlapping adjacent plates, sometimes compound, either fused with rostrolaterals or missing and formed of fused rostrolaterals; simple or compound with or without radii on each side [McLaughlin, 1980].

A beak-like structure projecting anteriorly from the carapace [Mauchline, 1984].

A median outgrowth of the anterior frontal region forming a signal or two distinct horns [Ingle, 1983].

A projection of the cephalic frons that may also include the dorsal surface of the cephalon. (Pl. rostra) [Wilson, 1989].

An anterior projection of the carapace that usually extends beyond the head region [Brusca and Brusca, 2002].

Anteriomedian projection of the carapace between the eyes (Fig. 1). (Pl. rostra) [Perez Farfante and Kensley, 1997].

Anteriorly projecting, unpaired, usually rigid median extension of carapace between eye or eyestalks; in cirripeds (Thoracica) unpaired valve between laterals and opposite carinal at basiscutal end of capitulum, simple and provided with alae in lower balanomorphs but compound and overlapping laterals in higher balanomorphs. See: compound rostrum [Moore and McCormick, 1969].

Anterodorsal projection of carapace [Holdich and Jones, 1983].

Dorsomedian anterior projection of cephalothorax, in crayfishes partly covering eyestalks and bases of antennae and antennules [Hobbs and Jass, 1988].

Prolongation of median part of anterior carapace between eyes [Poore, 2004].

The "head spine" or anterior projection of cephalothorax between the eyes of shrimps. (Pl. rostra) [Butler, T.H.].

The "head spine" or anterior projection of the cephalothorax between the eyes of shrimps or crayfishes. (Pl. rostra) [Chace and Hobbs, 1969].

The anterior projection of the cephalothorax between the eyes [Hobbs, Hobbs, and Daniel 1977].

(Order Cladocera):

Anterior (ventrally directed) extension of head. Relative length compared to antennules and antennae may be of taxonomic importance. (bent into hook, curved forward, recurved, straight; acute, blunt) [Stachowitsch, 1992].

(Order Diplostraca):

Prolongation of anterior end (underside) of head; located in front of upper lip (labrum) and therefore occasionally termed epistome. (armed, unarmed; acute, notched, pointed, rounded, spatulate = spatuliform, subtriangular). (Syn. frontal process, rostral process, beak) [Stachowitsch, 1992].

(Order Tanaidacea):

Relatively short anteromedian extension of carapace [Stachowitsch, 1992].

(Order Decapoda):

Unpaired anterior extension of carapace. Projects between eyestalks (ocular peduncles) and represents extension of frontal region. (compressed, depressed; acute, arched, circular, deflexed, obsolete, obtuse, sinuous, straight, triangular; tip: attenuate, bifid, bifurcate, styliform, subtruncate, truncate, upturned; unarmed, armed: ciliated, spinuliferous, toothed, tridentate, trifid) [Stachowitsch, 1992].

(Order Amphipoda):

Unpaired, immovable anterior extension of head between bases of antennules. (deflected, spine-like, triangular) [Stachowitsch, 1992].

(Order Isopoda):

Anterior median extension of head (cephalon) [Stachowitsch, 1992].

(Order Isopoda):

Anterior middorsal projection of cephalon [Kensley and Schotte, 1989].

(Order Isopoda):

Anteromedial projection of frontal margin of cephalon [Wetzer et al. 1997].

(Order Mysida):

Unpaired, imovable anterior extension of carapace. (pointed, rounded, simple, serrate) [Stachowitsch, 1992].

(Order Stomatopoda):

Unpaired, flattened anterior projection of carapace; relatively small, movable, and partially or entirely covering acron and antennular somite. (elongate triangular, subquadrate, subtriangular, triangular; with/without carina; deflexed). (Syn. rostral plate) [Stachowitsch, 1992].

(Order Leptostraca):

Rostral plate [Stachowitsch, 1992].

(Subclass Cirripedia):

() [Anderson, 1980].

^{Balanus trigonus: wall plates, exploded; and interior of operculum. [Anderson, 1980]}

(Subclass Cirripedia):

Barnacle shell plate: unpaired anterior plate. In stalked form, anteroventral plate on capitulum. In asymmetrical unstalked form, compartmental plate between carina and fixed scutum. In symmetrical unstalked form, anterior compartmental plate with median paries and lateral alae (simple or true rostrum) or with median paries and lateral radii (compound rostral plate: formed by fusion of rostrolaterals with rostrum or by fusion of rostrolaterals, with rostrum missing) [Stachowitsch, 1992].

(Subclass Copepoda):

The unpaired frontal projection of the dorsal cephalic shield, located between the antennules [Boxshall and Halsey, 2004].

(Class Ostracoda):

Anterior gaping, beak-like extension of carapace. Serves, along with associated rostral notch, to permit protrusion of antennae when valves are closed. (See also beak) [Stachowitsch, 1992].

(Class Ostracoda):

Anterior projection of valves of many myodocopans, overhangs incisur [Cohen, Peterson, and Maddocks, in press].

(Class Ostracoda):

Anteriorly projecting part of cephalic shield; may fold over anterior margin. (paired, unpaired; pointed, long, short) [Stachowitsch, 1992].

(Superorder Syncarida):

Unpaired, unmovable anterior extension of head (cephalon). (deeply cleft, quadrate, strap-shaped, ventrally deflected) [Stachowitsch, 1992].

(Order Euphausiacea):

Unpaired, immovable anterior extension of carapace; projects between eyestalks (ocular peduncles). (absent, obsolete, weakly produced, reaching/not reaching beyond eyes; acute, triangular) [Stachowitsch, 1992].