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Show 8 PROF. E. R. LANKESTER ON THE CARDIAC [Jail. 16, just above tbe suture, and a line of spots in tbe pale interval on last whorl; spire attenuate; suture well impressed; whorls /, sides well rounded; aperture ovate; the ridge in the centre of the columellar margin. The basal portion of a previous aperture may be noticed occasionally in young specimens of Melania. Size:- Maior diam. 1*6, alt. apert. 1*3, alt. axis 4*0 millim. „ „ 0*06, „ 0*05, „ 0*16 inch. EXPLANATION OF THE PLATES. PLATE I. Figs. 1, la, \b. Planorbis exustus, var. maculatus, p. 3. 2, 2 a, 2 b. cockburnii, n. sp., p. 4. 3, 3 a, 3 b, 3 c. Planorbis socotrensis, n. sp., p. 3. 4, 5. Hydrobia (?) balfouri, n. sp., p. 4. PLATE II. Figs. 1, 1 a, 2, 3. Melania scabra, pp. 5, 6. 4, 5, 6. tuberculata, p. 5. 7, 8. sclateri, p. 7. 9, 10. pagoda, pp. 6, 7. 11. amarula, p. 7. 2. On the Right Cardiac Valve of Echidna and of Ornithorhynchus. By E. R A Y LANKESTER, M.A., F.R.S., Jodrell Professor of Zoology in University College, London. [Eeceived January 14, 1883.] (Plates III. & IV.) Since I had the honour of placing before the Society the results obtained by the examination of the hearts of two specimens of Ornithorhynchus in last June (Proc. Zool. Soc. 1882, p. 549), I have been enabled by the kindness of friends to extend m y observations upon the structure of the right cardiac valve in the Mono-tremata. On the one hand, Professor Flower has very kindly allowed me to examine the hearts of two specimens of Echidna australis belonging to the museum of tbe Royal College of Surgeons ; and on the other hand, the late Professor Frank Balfour placed in my hands six specimens of Ornithorhynchus paradoxus preserved in spirit, whilst an additional specimen of the heart of Ornithorhynchus (making nine in all) was communicated to m e by Dr. Pye Smith. Additional Specimens o/Ornithorhynchus-Aearte.-In m y former paper it was shown that the right cardiac valve differed considerably in the twoOrnithorhynchus-henrta then described; and it was inferred, from the descriptions given by those authors, that the hearts examined respectively by Owen and by Gegenbaur differed in respect of their right cardiac valve from either of the hearts examined by me. Heart No. 1 of m y former paper presented, besides a large anterior |
