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Marcus, 1948

Overview
Diagnosis: Leucolesma corderoi Marcus, 1948 is charcterized by (1) absence of a copulatory bursa, (2) presence of a musculo-parenchymatic organ, and (3) a posterior position of the ovaries.
Habitus: Oval-shaped body, resembling the leaf of the coca plant; front end bluntly pointed and hind end sharply pointed; the living animal was about 3 mm long and 1 mm wide (Marcus 1948). From the sections it is apparent that the dorsal surface is pigmented, but the original description provides no information on the pattern of pigmentation.

Alimentary System
The pharynx lies in the posterior half of the body and is about one-fifth of the body length. The inner circular muscle layer of the pharynx is considerably thicker than the outer circular muscle layer. The mouth opening is at the hind end of the pharyngeal cavity.
The anterior ramus of the intestine extends as an undivided branch in front of the eyes. The anterior gut trunk gives rise to about 9 pairs of postocellar diverticula. Each of the caudally running gut trunks gives off about 12 lateral diverticula; the posterior rami unite in the hind end of the body.

Male Reproductive System
There are 3-4 testes on either side of the body, occurring between the ovaries and the root of the pharynx; the rather small follicles are situated ventrally.
The vasa deferentia expand to form wide false seminal vesicles, which even increase further in size where they enter the penis, thus forming accessory seminal vesicles. The latter join in the proximal part of the penis papilla to form a narrow ejaculatory duct.
The penis papilla is a stubby, vertically oriented cone which is lined with a flat, nucleate epithelium. A coarse-grained, erythrophilous secretion is abundantly present in the penis papilla. A penis bulb could not be discerned.
The male atrium communicates via a narrowing with the small, and ciliated common atrium.

Female Reproductive System
The vitellaria occur from a short distance behind the brain into the hind end of the body; they extend from dorsal to ventral body surface.
The ovaries are positioned between one-third and one-half of the distance between the brain and the root of the pharynx, medially to the ventral nerve cords. The oviducts arise as broad tubae from the anterior surface of the ovaries, but it was impossible to trace their course backwards in the material examined. Caudally to the gonopore the oviducts unite to a rather long common oviduct, which runs anteriad to open into the common atrium. The common oviduct is lined with nucleate cells and receives the openings of shell glands.

Musculo-parenchymatic Organ
The postero-dorsal wall of the common atrium gives rise to a large, tube-shaped indentation with a mushroom-shaped chamber at its distal end. The entire indentation is lined with nucleate cells. This indentation is surrounded by a very thick, pear or egg-shaped zone of muscles, leaving free only a narrow parenchymatic zone around the tubular section of the indentation. The musculature of the organ mainly consists of strong, circular fibres.

Eyes
The pigment cups are provided with a rounded lens. In contrast to Marcus (1948) I found it impossible to establish the number of retinal cells in the eye cup.

Ecology
The type and only known specimen was collected from among algae near Santos, Brazil.

Distribution
Type locality: Bay of Santos (23°56'S 46°22'W), ilha das Palmas, Brazil. The species is known only from the type locality.

Material Examined, Type Material
S.M.N.H.: Bay of Santos, ilha das Palmas, Brazil, sagittal sections on 1 slide.

Leucolesma corderoi