Gomphosinica geitleri

Valves are clavate, with a broadly rounded to subrostrate headpole. The footpole is narrow and rounded. The axial area is narrow. The central area may be transverse or round and contains a single stigma. The raphe is slightly undulate and lateral. Distinct helictoglossae are present near both apices. The striae are radiate near the central area, becoming nearly parallel near the valve ends. One to two striae distal to the helictoglossae are radiate. Some striae near the central area are irregular and shortened. An apical pore field is present at the footpole.

In the SEM, the valve exterior is covered with round areolae, organized into multiseriate striae. The striae are biseriate, to arranged in a quincunx near the axial area. Externally, the proximal raphe ends are straight. At the headpole, the distal raphe fissure is straight; at the footpole, the distal raphe fissure extends over the mantle and bisects the apical pore field. The stigma has a simple, round external opening. The apical pore field is composed of small, round porelli. Internally, a reduced pseudoseptum is present at the headpole. The striae are located in depressed chambers; an axial plate and marginal lamella are both absent. The proximal raphe ends are recurved at the central nodule. The internal expression of the stigma is multichambered. Distally, the raphe terminates at distinct helictoglossae. The apical pore field has depressed chambers.

The specimens presented here represent the range of one population - large initial valves to valves smallest end of the size range.