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VI. On thirty-one Species of Marine Planarians, collected partly by the late Br. Kelaart, 

 F.L.S., at Trincomalee, and partly by Dr. Collingwood, F.L.S., in the Eastern 

 Seas. By Dr. Collingwood. 



(Plates XVII. to XIX.) 



Read March 18th, 1875. 



Contents. 

 I. Prefatory and introductory. 

 II. Characters of two new genera of Euryleptidas. 

 III. Synopsis of the genera and species described and 

 figured in the present paper. 



IV. Description of twelve new species of marine Pla- 

 narians collected by Dr. Collingwood, and deli- 

 neated in the accompanying figures. 

 V. Dr. Kelaart's descriptions of his figures of marine 

 Planarians collected in Ceylon. 



I. 



1HE species of Planarians which I ana about to lay before the Society were, as far 

 as I was concerned, the fruit of many searches upon rocky shores of the coast of China, 

 Borneo, Singapore, &c, and represent a considerable amount of labour near low- 

 water mark in turning over stones, pieces of coral, &c. in such situations. The little 

 animals in question, although extremely interesting, are all more or less minute ; and it 

 requires not only a sharp but an educated eye to discover them ; for so delicate are they, 

 and often so thin in texture, that out of the water, and adhering to a more or less muddy 

 or weed-grown stone, it is by no means easy to detect them. It must not be under- 

 stood, however, that these searches were unrewarded except by the comparatively small 

 number of specimens or new species here recorded. Many other animals of interest 

 divided the attention, as, for instance, nudibranchiate Mollusca, of which a number 

 of new species await the notice of the Society, and other no less interesting creatures. 

 The Planarians in many respects rival the Nudibranchs in gracefulness of form and 

 beauty of colouring ; but they are even more delicate than the latter. When a small 

 spot of colour upon the under surface of a stone betrays the presence of one of these 

 little animals, a camel's-hair brush is necessary to dislodge it safely ; and a bottle of salt 

 water must be at hand, into which to transfer the prize. 



It may be thought that a dozen species is but a small number to reward one's labour 

 on coasts which are supposed to abound with unknown forms of animal life. But 

 a good deal of experience in shore-hunting on our own coasts prepared me for the 

 fact, which I found amply corroborated on foreign shores, that we must not look for 

 a large number of species at any one locality, unless the same locality is examined many 

 times, and at different seasons of the year — conditions not always, or, indeed, often 

 practicable. These little organisms appear to be sporadically distributed over wide 

 areas. They are seldom met with gregarious; and three or four species captured upon 

 any given occasion might be reckoned a prize more than ordinarily satisfactory. 



SECOND SERIES. — ZOOLOGY, VOL. I. N 



