In these batrachians the pectoral arch falls into two distinct types - the arciferous, in which the precoracoid (+clavicle) and coracoid are widely separated from each other distally and connected by an arched cartilage (the epicoracoid), the right usually overlapping the left; and the firmi- sternal, in which both precoracoid and coracoid nearly abut on the median line, and are only narrowly separated by the more or less fused epicoracoids.
A fine cylindrical rod or fibre (the so-called solid axis or virgula) becomes developed in a median groove in the dorsal wall of the polypary, and is sometimes continued distally as a naked rod.
Each cone consists of an axis, on which numerous broad and thin bracts are arranged in regular rows; in the axil of each bract occurs a single flower; a male flower is enclosed by two opposite pairs of leaves, forming a perianth surrounding a central sterile ovule encircled by a ring of stamens united below, but free distally as short filaments, each of which terminates in a trilocular anther.
A typical male flower consists of a central axis bearing numerous spirally-arranged sporophylls (stamens), each of which consists of a slender stalk (filament) terminating distally in a more or less prominent knob or triangular scale, and bearing two or more pollen-sacs (microsporangia) on its lower surface.
Foot expanded distally into a symmetrical disk with a crenate edge or simple and vermiform without well-developed lateral processes; shell often contracted towards the anterior aperture.