THE MARINE TURBELLARIA, 



WITH AN ACCOUNT OF THE ANATOMY OF SOME OF THE SPECIES. 



By Frank Fortescue Laidlaw, B.A. (Cantab.), Demonstrator and Lecturer 



in the Owens College, Manchester. 



(With Plates XIV. and XV. and Text-Figiires 61—73.) 



CONTENTS. 



PAGE 



I. Systematic List, with Notes on the Anatomy of the Species ..... 282 



Planoceridae — Leptoplanidae — Cestoplanidae — Pericelidae, nov. fam. — Pseudoceridae — 

 Prosthiostomidae. 



II. Notes and Conclusions 303 



Planocera and a new Genus — Thysanozoon and Thyaanoplana — Distribution in the 

 Indian Ocean — Parasites — Gut Diverticula — Relationships of the Cotylea — Co- 

 tylea and Acotylea — Origin of Nuchal Tentacles — Natural History Notes. 



III. Literature 310 



I. SYSTEMATIC LIST, WITH NOTES ON THE ANATOMY OF THE SPECIES. 



ACOTYLEA. I. Family Planoceridae. 



1. Planocera armata, sp. n. (PL XV. figs. 10, 11, and 12). 



One specimen fi-om 40 fathoms, Suvadiva Atoll. Rubble and broken coral bottom. 



Total length about 25 mm., total breadth about 15 mm. Tentacles from ant. margin 5 mm. 

 Mouth aperture about 13 mm. behind anterior margin. Male gonopore about 5 mm. behind 

 mouth. Female gonopore about 1 mm. behind male. 



Colour white with small pigmented patches, scattered rather numerously near the dorsal 

 surface. Tentacles about 2 mm. apart, bilobed at the tips; each with a dense cluster of eyes 

 at its base. Brain compact, lying under a median branch of the gut. There is a cluster of 

 eyes over the brain between the tentacles (Fig. 61). 



