BRITISH MARINE TURBELLARIA. 239 



the female genital pore. The male copulatory organ consists of a 

 ductus ejaculatorius, and the strongly muscular vesiculte seminalis and 

 granulorum. The ova scattered throughout the body accumulate after 

 fertilisation in the long uterus, which completely (in adult specimens) 

 surrounds the pharynx and genital-apparatus. The uterus communi- 

 cates with the exterior by a median duct, which in its lower portion 

 is surrounded by the voluminous " shell-gland." 



Habitat. — Firth of Forth (Dalyell) ; Cultra, Belfast Bay (W. 

 Thompson) ; Rothesay (Johnston) ; Firman Bay, Guernsey (Ray 

 Lankester) ; St. Andrews (Mcintosh) ; Jersey, Guernsey, Herm 

 (Koehler) ; Plymouth Sound and neighbourhood, from littoral zone to 

 20 fms. (W. Garstang, F. W. G.) ; Hilbre Island, mouth of the Dee, 

 Port Erin, Isle of Man (F. W. G.) ; Aberystwyth (J. H. Salter). 



Distribution. — Black Sea, Mediterranean, west coast of France, 

 coast of Holland, Denmark, Baltic, North Sea, Red Sea. 



The distinctive peculiarities of this species are the possession of a 

 "sucker" and the simplicity of the female copulatory organ. Thus 

 the "antrum femininum," or cavity into which the female genital 

 pore leads directly, remains simple, while in Leptoplana alcinoi and 

 vitrea its walls are very muscular, and the organ becomes a bursa 

 copulatrix. External form and colour, as Lang has forcibly stated 

 (54, p. 482), afford no secure basis for the foundation of characters by 

 which the species of Leptoplana may be distinguished. 



63. Leptoplana Mertensii (Claparede). 



1861. Centrostomum Mertensii, ClapaHde (35). 



Length 18 mm. Body oval, white, or yellowish. Two groups of 

 eyes on the dorsal surface. 



As no details as to the structure of the genital organs are given, it 

 is impossible to satisfactorily assign a position to this species. 



Habitat. — On Laminaria, Lamlash Bay, Arran (Claparede). 



APPENDIX TO LEPTOPLANIDiE. 



64. Planaria atomata, 0. F. Mtiller. 



1777. Planaria atomata, 0. F. Milller (4). 



1823. „ „ Fleming (8). 



1839. „ „ Forbes aud Goodsir (13). 



