Figure 1 - Marshallia tortuosa, Alemannia, Höver.
Basal section and stem.

Figure 2 - Marshallia tortuosa, Alemannia, Höver.
Mid section, viewed from below.

Figure 3 - Marshallia tortuosa, Alemannia, Höver.
Stem and root processes.

Figure 4 - Marshallia tortuosa, Alemannia, Höver.
Top section with smooth brim.

Figure 5 - Marshallia tortuosa, Alemannia, Höver.
Top section with a sinuous margin.

Synonyms:

Pleurostoma tortuosa Roemer 1864
Spirolophia tortuosa Pomel 1872

Occurence:

Alemannia, Höver, Lower Campanian (senonensis zone). Rare.

Marshallia tortuosa is a moderately rare species of the Lower Campanian of Höver. Apparently, a second Marshallia species exists, which occurs in both the Lower Campanian of Höver and the Upper Campanian of Misburg. It will be described informally below.

Marshallia tortuosa has a very characteristic twisted habit (Figures 1, 2, 4 and 5), resulting from a spiralling arrangement of longitudinal (actually oblique) folds in the funnel wall. The individuals can look quite different, depending on the number of folds, which can range from two to at least five. The specimen shown in Figure 1 has three folds and a slender habit, while that in Figure 2 has five folds and a flat shape.

Marshallia tortuosa has a proper stem with laterally radiating roots at its base (Figures 1 and 3).

In its lower sections, the fold crests of Marshallia tortuosa show accessory oscula, which are circular and 3 to 4 mm in diameter (Figures 1 and 4). Near the upper end of the sponge, intercalated secondary folds may develop (Figure 4).

The upper brim of Marshallia tortuosa may be smooth as in Figure 4, or sinuous as in Figure 5.

Figure 6 - Marshallia tortuosa, Alemannia, Höver.
Gastral surface, etched specimen.

Figure 7 - Marshallia tortuosa, Alemannia, Höver.
Dermal surface, etched specimen.

Figure 8 - Marshallia tortuosa, Alemannia, Höver.
Dermal surface viewed from outside.

Figure 9 - Marshallia tortuosa, Alemannia, Höver.
Dermal layer viewed from inside sponge wall, etched specimen.

Figure 10 - Marshallia tortuosa. Alemannia, Höver.
Cross section through sponge wall. Etched specimen.

Both surfaces of Marshallia tortuosa are fortified by a siliceous cortex.

On the gastral surface, this cortex consists mainly of an additional silica manteling of the uppermost lychnisk layer, i.e., all rectangular meshes are open (Figure 6). However, minor areas may exist where the gastral cortex resembles that of the dermal surface (Figure 6).

The dermal cortex (Figures 7 to 9) is different, with every second rectangular mesh being filled with a siliceous membrane containing several small pores. The filled and unfilled meshes alternate in a very regular manner, such as the fields of a chess board.

Figure 10 shows a cross section through the wall of Marshallia tortuosa, showing the very regular internal (dictynal) skeleton composed of fused lychnisks, as well as the fortified dermal and gastral cortex layers.

Figure 1 - Marshallia sp., Teutonia, Misburg.
Basal section with "becksia-type" hollow side roots.

Figure 2 - Marshallia sp., Alemannia, Höver.
Basal section with hollow side roots.

Synonyms:

none  

Occurence:

Teutonia, Misburg, Upper Campanian (spiniger zone). Rare.

Alemannia, Höver, Lower Campanian (senonensis zone). Rare.

A second kind of Marshallia can be found in both, the Lower and Upper Campanian of Höver and Misburg. Apparently, this species was already known to Schrammen (1912) since, in his description of Marshallia tortuosa, he mentions "Becksia-type" tubiform root processes emerging from the side of the fold crests, but also parietal oscula on the crests (,and this has led to some confusion in the past). However, according to the author's observations both features never occur together in one and the same specimen. Parietal oscula are associated only with specimens having a stem and laterally radiating roots at their very ends (see Figures 1 and 5 of M. tortuosa above).

The lateral roots of Marshallia sp. are 3 to 5 mm thick and quite long (50+ mm), as seen in Figures 1 and 2. The lateral roots are essentially hollow tubes which are derived from the dermal cortex.

The skeleton of Marshallia sp. is indistinguishable from that of Marshallia tortuosa.