1. British marine Turbellaria, as at present known, include about fifty-seven species of Rhabdocœlida, twelve of Polycladida, and two Tricladida, making a total of seventy-one species. The numbers represent the examination of a limited extent of our coast (Millport, St. Andrews, Skye, the Isle of Man, Plymouth, and Channel Islands) during about three months of the year (July to September).

2. The following twenty-eight species are added to the British fauna in the present paper.

POLYCLADIDA :

Cycloporus papillosus, Lang.

ACŒLA :

Proporus venenosus (O. Sch.).

Monoporus rubropunctatus (O. Sch.).

Aphanostoma elegans, Jensen.

RHABDOCŒLA :

Promesostoma ovoideum (O. Sch.).

" solea (O. Sch.).

" agile (Lev.).

" lenticulatum (O. Sch.).

Byrsophlebs Graffi, Jensen.

Mesostoma neapolitanum, v. Graff.

Hyporhynchus armatus (Jensen).

? " penicillatus, (O. Sch.).

Provortex rubrobacillus, n. sp.

ALLŒOCŒLA :

Plagiostoma dioicum, Metschnff.

" sulphureum, v. Graff.

" Girardi (O. Sch.).

" pseudomaculatutn, n. sp.

" sagitta (Vlj.).

" elongatum, n. sp.

" caudatum, Lev.

" (?) siphonophorum (O. Sch.).

Vorticeros luteum, v. Graff.

Cylindrostoma inerme, Halley.

" elongatum, Lev.

Monoophorum striatum (v. Graff).

Monotus albus, Lev.

Automolus horridus, n. sp.

" ? ophiocephalus (O. Sch.).

3. The relations of the Turbellarian fauna of our coasts with that of neighbouring seas cannot be determined with certainty until more extended observations are recorded than we possess at present. Mediterranean and Adriatic forms occur on our south-western stations (Plymouth, &c.). Thus seven Polyclads and sixteen Rhabdocœles (33 per cent, of our fauna) are common to Naples, Trieste, and Plymouth. A large proportion (about 70 per cent.) of Scandinavian forms occur on our coast.

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