Plumatella crispa Wood 2022, n. sp.

Plumatella crispa n. sp.

(Fig. 15)

Holotype. ZSI P163 collected 1 January 1922 in “ Canton, China ” by A.W.L. Oliver, originally labeled “ Plumatella fruticosa ”.

Diagnosis. The colony appears as a tangle of free branches; dorsal margin of the floatoblast slightly curled inwards.

Etymology. The specific epithet is from the Latin adjective crispus, meaning curled or curly, in reference to the upturned dorsal margin of the floatoblast.

Description. Colony appearing as a tangle of branching tubules extending from the substratum; floatoblasts long and narrow (Table 1), floatoblast dorsal fenestra relatively small, with length and width less than half of corresponding outer dimensions of the floatoblast; tubercles on the dorsal fenestra low and rounded, with little space between them, dorsal valve margins distinctively scalloped or lightly curled; floatoblast ventral fenestra broadly oval, nearly twice as wide as the dorsal fenestra, with low, rounded tubercles that fade towards the center.

Distribution. The species is known only from its type locality in China.

Remarks. The holotype colony is attached in places to a small piece of reed. Sessoblasts are absent. The marginal curling of the floatoblast is best seen with scanning microscopy, but is nevertheless detectable when the isolated valve is viewed with a compound microscope. The initial designation of this species as Plumatella fruticosa is understandable, since colonies of both species have free branches, the floatoblasts are long and narrow, and the dorsal fenestrae are relatively small. An important difference is one of scale: with P. fruticosa the floatoblast length is over 500 µm (Fig. 20b), while in P. crispa n. sp. it is less than 400 µm.