288 DE- H. J. FLETJEE ON THE EVOLUTION OF 



40. Pelseneer, p. — Recherches morpliologiques et pliylogenetiques sur les MoUusques archaiques. 



Mem. cour. etc. pub. par I'Acad. Roy. de Belgique, t. Ivii., 1899. Also references in other papers. 



41. Perriek, Remy. — L'anatomie et Thistologie du reiu des Gasteropodes prosobranches. Aun. Sci. 



Nat., Zool. ser. 7, t. viii., 1890. 



42. P11.SBRY, W. H. — Tryon's Manual of Concliology. Continued by Pilsbry. Marine Univalves, 



vol. xiii. 



43. ScHOFiELD (and Ulrich). Geological Survey of Minnesota, vol. iii. pt. 2. " Lower Silurian 



Gastropoda." 



44. SiMROTH. — MoUusca. Bronn's Klassen und Ordnungen des Tierreichs. 



45. Sprengel, J. "W. — Die Geruchsorgane und diis Nervensystem der Mollusken. Zeit. f. wiss. Zool. 



Bd. x.^xv., 1881. 



46. Thiele, J. — Die systematische Stellung der Solenogastren und die phylogenie der Mollusken. 



Zeitsclir. fiir wiss. Zool. Ixxii. (In tliis paper will be found a complete list of the author's 

 previous publications dealing with Molluscan morphology.) 



47. Tryon, G. W. — Manual of Conchology. Continued by W. H. Pilsbry. See Pilsbry, W. H. 



48. Ulrich and Sciiofield. — "Lower Silurian Gastropods." Geol. Survey Minnesota, vol. iii. pt. 2. 



49. Wegmann, H. — Notes sur I'organisation de Patella vu'gata. Rec. Zool. Suisse, t. iv., 1887. 



50. Willcox, (Miss) M. A. — Zur Auatomie von Acmtea fragilis. Jenaische Zeitsch. f. Naturw. 



Bd. xxxii., 1898. 

 CI. Willcox, (Miss) M. A. — Notes on the Anatomy oi Acmcea testudinalis. ' Science,' vol. xi. 



52. WiLLEY, A.— Tidal Migrations of Patella. ' Nature,' liv. 1896, p. 125. 



53. Williams, T. — On the Mechanism of Aquatic Respiration in Invertebrates. Ann. & Mag. Nat. 



Hist. ser. 2, vol. xvii. 1856, pp. 28-42, 14-2-154, 247-258. 



54. Woodward, S. P. — A Manual of the Mollusca. London, 1851. 



55. ZiTTEL, K. A. VON. — Haudbuch der Paliiontologie. 1 Abth. Palaozoologie, Bd. ii., Mollusken, 



1885. 



EXPLANATION OF THE PLATES. 



(iy«/7^.= Hypothetical.) 



Plate 15. 



Fig. 1. SheM oi Bellerophon ejrpansus. Wenlock Limestone, Dudley. 



2. Shell of embryo Acmtea showing vestige of spiral. 



3. The hypothetical Prostreptoneure, seen from the right side, the shell being supposed to be 



removed. 

 Figs. 4 & 5. Stages illustrating the transition to a Docoglossan type. 

 Fi". 6. A supposed dissection of the Prostreptoneure, from the left side. The gut and pericardium 



are shown as embedded in the general mass of the remaining organs of the body ; details of 



the latter are omitted for the sake of simplicity. 



7. Schematic diagram showing the settling-down of the viscera in the pro-Docoglossa in the 



second stage of consolidation of the visceral mass. 



8. The gut at the hypothetical stage represented in fig. 7. The rectum is only dotted in. 



(The letter Q in figs. 8-10 should be deleted.) 



9. The gut of Acmesa galathea. After Haller. 

 10. The gut of Ancistromesus. After Haller. 



