The Opisthobranchs dealt with in this paper were entrusted to me by Dr. C. O. van Regteren Altena, Rijksmuseum van Natuurlijke Historie, Leiden, and belong to that museum. They are part of a large collection of marine molluscs from Surinam of which Dr. van Regteren Altena intends to publish an annotated catalogue. The material was preserved rather badly, e.g. 3 specimens of Bornella calcarata had dried out and were hard and stiff. No descriptions or colour-notes on the living animals were available. These appear to be the first Opisthobranchs recorded from the Guianas. The drawings illustrating this paper were made by Mr. Jos Ruting, artist at the Zoological Museum at Amsterdam. ORDER NOTASPIDEA FAMILY PLEUROBRANCHIDAE Pleurobranchaea hedgpethi Tucker Abbott, 1952 (fig. 1-2) RNHL no. 6266; 1 specimen, Surinam, dredged by the "Coquette" on her 5th trip, 29.IV.-3.V. 1957, NNW of Marowijne river, 20 miles off the coast, depth 15 fathoms. The preserved animal (slightly contracted) is 15 mm long, 5 mm high, the foot 5 mm and the total animal 6 mm broad. The body has an oval shape. The foot protrudes behind, with a small firm dorsal spur that is about 0.6 mm high. The pedal gland measures 2 mm. The animal has a pale yellow colour with a few traces of brown mottling near the tail and on the tip of the right rhinophore. The mouth shows as a straight line between the jaws with dark coloured skin of the trunk surrounding it. The border of the frontal veil is very slightly tuberculated. The velum with tentacles is slightly pushed aside on top of the head by the strongly protruding trunk. The dorsal surface of the mantle is thin and minutely pimpled.