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expands as an opened groove. Outer lamina simple, with flap protecting nephrostome inserted in its posterior extremity. Inner lamina thicker, with a very long chamber running within its border, from region close rectum to its anterior third parł, where opens in a long furrow. Małe pallial sperm groove with inner surface morę complex than that of female, presenting some longitudinal folds posteriorly and obliąue folds anteriorly. Pallial gonoduct finishes close, but posterior to anus. No ovopositor differentiable.

Nervous system. Nerve ring (fig. 244) as normal cerithioideans and very similar to that described by Marcus & Marcus (1964) for Cerithium atratum. Connective between pedał ganglia short. Connectivebetween cerebral ganglia relatively long. Statocysts with several statolyths (statoconia).

Measurements (in mm). 42.4 by 15.2; 51.0 by 18.4; 36.7 by 13.8.

Distribution. French Guyana, Surinam, North Brazil (Amazon region).

Materiał examined. French Guyana; St. Takari Tante, Sinnamery River, 6 specimens, MZSP 28286 (INPA, 20/xi/1989).

Remarks. Doryssa atra resembles the shell characters of D. transversa (Lea, 1850) (fig. 13, a specimen from MZSP numbcr 28726, from Boa Vista, Roraima) from which differs in having broader shell and shorter spire, but, from the Brazilian Doryssa, that is which D. atra have morę aflinity.

Doryssa macapa (Moricand, 1856)

(Figs U, 60, 93,94, 254-264)

Melania macapa Moricand, 1856: 176 (pl. 6, fig.

7); Reeve, 1860 (pl. 29, fig. 194).

Doryssa macapa: Morretes, 1949: 75. Complement in Ihering, 1902: 663.

Description.

Shell (fig. 11). Of medium size, turriform, very eroded apex, only 4-5 last whorls present. Walls heavy, thick. Whorls outline almost straight, suture little evident. Sculpture strong axial threads (about 22 in penultimate whorl), each thread uniformly lobed by transversal furrows, giving an effect of spiral sculpture (about 6 in penultimate whorl). Between axial threads smooth surface. Last whorl with 6 or 7 spiral broad threads in pcri-um-bilical and siphonal regions (infenor) and axial threads with about 6 lobes (as above described) in superior region. Aperture simple, without canal, somewhat elliptical, posterior region strongly an-gular. Lips glossy, thick, simple. Periostracum dark brown, almost black, opaque.

Head-foot (figs 245-248). Color dark brown, almost black, posterior regions and foot sole beige. Head protmding, broad. Snout broad, short, dorso-ventTally flattened, anterior margin bilobed. Mouth longitudinal, antero-ventral, thick muscu-lar. Tentacles stubby, base broad. Ommatophore sessile in head, situated in outer, ventral region of tentacles base. Eyes dark, somewhat smali, in anterior extremity of ommatophore. Foot of medium size, without divisions; anterior furrow of pedał glands. Columellar muscle of about 1.5 whorls. Female with ovopositor described below.

Operculum (fig. 60). Similar to that of preceding Doryssa species,

Mantle organs (figs 257-259). Mantle border simple, without neither tentacles nor papillae; edge dark brown, gradually becoming elear with dark minutę spots posteriorly. Mantle cavity of almost two whorls. Siphon inconspicuous. Osphradium long, ridge-like, with about 1/3 of gili length; anterior extremity posterior than that of gili and preceded by a zigzag. Gili narrow and very long, about same length than pallial cavity; filaments triangular, Iow; tip rounded, almost central. Ctenidial vcin gradually becomes broad, in posterior region about same width than gili. Between gili and rectum a somewhat nanow area with some transversal, sparse vessels. Hypobranchial gland inconspicuous. Adrectal sinus very broad, rectum running ffee within it. Rectum broad, with several fecal pellets obliąuely disposed. Anus siphoned, posterior from mantle border. Genital duet in right margin described below.

Circulatory and excretory systems (figs 256, 258). Heart characters similar to those of preceding Doryssa species, aortas attached to style sac antero-dorsal region. Kidney short, about 1/4 whorl, almost entire solid, except a flattened chamber surrounding rectum; left surface of this chamber covered by uniform transversal folds without development of septa; right surface of this chamber with several transversal, not uniform folds (fig. 258), with irregular surface, attached to outer surface of rectum; thesc folds also present in anterior region of nephrostome. About half of kidney in pallial cavity