accumulation. The mode of reproduction has not yet been fully worked out, but the animals are bisexual and the genital ducts relatively simple, as in the lower prosobranchs in general. The landward migration of marine gastropods has become possible only in those that have evolved about the rhipidoglossan level, and in which the gametes are no longer discharged by way of the right kidney. Fertilisation now becomes internal, and a closed pallial genital duct has been developed. In the males the sperms are conducted forwards by a closed channel to a well-developed cephalic penis; in the female, a closed glandular oviduct, derived from secretory tissue of the pallial wall, runs forward to open alongside the rectum.

In Murdochia, the alimentary canal combines a primitive structure with certain specialised features. The absence of oesophageal pouches or other sources of enzyme secretion within the oesophagus is evidently an advanced feature, paralleling the condition described in the specialised Turritella (Graham, 1938). The salivary glands are likewise devoid of enzyme cells, and Murdochia would appear to have been singularly improvident in abandoning all its sources of extra-cellular digestive enzymes, probably before the landward migration of the family. Whether or not the spirochaetes in the protostyle have taken on an accessory role in digestion remains to be determined. The small size of the animal—as well as its primitiveness—may be a contributing factor to the simplicity of structure of the stomach. The loss of the ciliary sorting area is probably correlated with the terrestrial habit and the changed nature of the food. The primary function of the stomach is no longer sorting, but the breaking down, whether by digestion or mechanically, of particles of plant material still too large for entry into the digestive diverticulum. The extreme posterior position of the opening of the oesophagus into the stomach is to be regarded—following Graham (1949)—as a highly primitive feature. In almost all other mesogastropods it has migrated some distance forwards towards the intestinal aperture. The long, backwardly directed sac in the stomach of Pomatias (Graham, 1939), Littorina (Graham, 1949), Melarhaphe and Risellopsis (present writer, unpublished), would appear to be directly homologous with the cuticulate chamber of the stomach in Murdochia, after the forward migration of the oesophagus, to open shortly behind the style sac—intestinal chamber. In Murdochia, the formation of firm, mucusbound faecal pellets in the intestine is a relic of ancestry among marine prosobranchs, where the compacting of the faeces serves as a device for prevention of fouling of the respiratory water of the pallial cavity. In a terrestrial prosobranch it is probably equally necessary in the absence of a cleansing current passing continuously through the pallial cavity.