1908.] ASPIDOBRAXCH GASTROPOD MOLLUSCS. 835- 



rintestin et du sac radulaire dans la region, anterieure du corps 

 et se prolonge en arriere jusqii'a 1' origine du rein.'"' This 

 description is tolerably exact, but the ramifications of the coelomic 

 ca.vity are extremely difficult to make out in Neritina, and a much 

 clearer picture o£ the extent and relations of the coelom can be 

 obtained fi-om the more symmetrical Septaria. In this genus, as 

 may be seen in fig. 4, the ccelom is, relatively to the size of the 

 body, a vast space extending from right to left across the entire 

 width of the visceral mass. 



Two divisions can be recognised, the pericardial and the gonadial 

 ccelom. The former lies to the left ; it is traversed by the bend 

 of the rectum, contains the heart, and communicates by the reno- 

 pericardial duct with the kidney. The gonadial division of the 

 ccelom lies on the right, and may be described in general terms 

 a,s intervening between the liver and ovary and the dorsal body- 

 wall in the region of the visceral mass (fig. 4, g.co.). Near the 

 anterior border of the visceral mass it forms a spacious cavity 

 extending downward on the right side of the body to the level of 

 the floor of the visceral hfemoccele, and here it enters into 

 remarkable relations with the oviduct. As shown in figs. 3, 4^ 

 and 5, the oviduct, which pursues a nearly straight course forward 

 from the ovary to the accessory genital apparatus, crosses the 

 gonadial coelom, and at this point opens into it by a distinct 

 but short and narrow oviduco-coelomic duct, the details of 

 which are indicated in fig. 5. The duct is lined by a cubical 

 epithelium bearing fine cilia, and this, near its opening into the 

 gonadial division of the coelom, is replaced by an epithelium 

 containing closely crowded, deeply stained nuclei and bearing 

 longer cilia. The similarity between this oviduco-coelomic funnel 

 and duct and the reno- pericardial canal of the left side is obvious, 

 and afibrds evidence of the former existence of a right kidney, 

 into which, as in other Rhipidoglossa, the ova were discharged to 

 find their way to the exterior by the right uropore. The full 

 significance of these relations will be dealt with further on : it 

 need only be said here that the existence of an oviduco-coelomic 

 funnel, opening into a special division of the coelom, is not 

 parallelled in any other adult Gasbropod, except the allied genera 

 JVerita and Neritina. 



The pericardial division of the coelom is of large size : it extends 

 forward to the base of the ctenidium and is continued for some 

 little distance along the left edge of the lattei', parallel to the 

 efferent branchial vessel, as a narrow diverticulum. Posteriorly 

 the pericardial cavity extends along the left side of the stomach 

 nearly to the pointed extremity of the visceral mass. The 

 gonadial division of the coelom is a more irregular cavity. In the 

 anterior part of the visceral mass, immediately behind the 

 accessory genital organs, it is of considerable vertical depth, 

 reaching from roof to floor of the visceral sac in front of the 

 liver and ovary. A little further back it extends over the liver 

 and ovary and to the right of the latter as far as the floor of the 



