Corallum consists of tall, misshapen, anastomosing stems of branches arising from a small base; stems and branches irregular in diameter throughout their length, curving and twisting in disorderly fashion. Segments of same stem may be almost cylindrical or flat at different levels. The twisting is accentuated by the course of septocostae. One stem with only one branch has these dimensions; 11 x 8 mm across at basal segment, 6 x 5.5 mm segment at next segment, 6 x 4 mm at following segment, and 8 x 3 mm below tip. Surface appears rough because of unevenness of septocostae, but may be smoother on lower side of recumbent stem. Tips of terminal branchlets mostly flat.
Corallites unequal in size according to age. One at base of branch 11 x 14 mm across (distance from beginning of costa on one side to corresponding point on opposite side, across middle of columella); another one point of same branch 6 x 8 mm; much smaller one near tip. Generally a corallite situated at fork of a branch. Corallites slightly elevated – exsertion of septa brings about this.
Prominent septa 12 to 18 in mature corallites (less in immature ones), most of those attached to columella conspicuously thickened, exsert, their septal spines (if present) tall and rough. Coalescence of thin higher cycle septa with those of lower cycle quire obvious. Septa somewhat markedly lowered as they run out of calice and become continuous with costae (or septocostae). Septal spines on edge and surface more abundant inside calice, thinning out outside.
Septocostae completely cross intercalicinal areas; higher, thicker (thickness uneven) ones with more conspicuous spinules regularly alternating with lower, thinner ones with finer spinules. Courses of septocostae winding on almost cylindrical lower segments of branches, becoming almost longitudinal on flattened terminal portions of branchlets.
Columella in large corallites prominent, usually oval in shape, a crowded mass of horizontal platelets with cut edges producing tiny tubercles. In small (young) corallites, columella may be absent so septa from opposite sides may cross calicinal center.
There are several specimens of this species brought in from Arangasa islet. Their manner of branching varies from predominantly vertical stems with few points of coalescence (C-228) to branches growing in all directions (C-33). Some (C-238) produce at the base a plate-like branch with a corallite at the center and several branchlets issuing forth at the side.
This species is distuinguished from P. (Parapectinia) teres sp.n. also described in this paper by its misshapen appearance, rough surface and noncylindrical branches.
