30 BRITISH Tl'NICATA. 



or level surface for the support of the branchial sac, which 

 otherwise might suffer from the inequality produced by the 

 genitalia. These peculiar organs are found in all the ( ']/nth iadtf 

 that have been examined, including Pelonaia ; and in all the 

 reproductive organs project boldly from the surface of the 

 mantle. 



This arrangement of the reproductive organs also occurs in 

 Sti/da nianilllarls, and in two undescribed species ofthe genus, 

 recently obtained by the Rev. A. M. Norman at Guernsey. 



In Thylachint (j</r<'i/ntnm the same disposition of these parts 

 is also found to exist. 



In Cynthia orata, an undescribed species allied to C. *<iuamn- 

 lo*a, we have a very remarkable modification of these organs. 

 Here there are only two generative masses one placed im- 

 mediately above the alimentary tube, the other within the 

 intestinal loop. They are elongated and fusiform, each being 

 composed of a double parallel series of squarish nodules in 

 which both ovary and testis are combined. Each mass has 

 its own proper oviduct and i-as deferens, which pass forward, 

 united, between the series of nodules, and, extending a little 

 way in advance of the organ, open into the cloaca near to the 

 anal orifice. 



But perhaps the most interesting variety of this apparatus 

 occurs in Pelonaia, in which there are two elongated tubular 

 ovaries, each being bent so as to form a wide loop ; they are 

 attached throughout to the mantle, and bulge out the lining 

 membrane; one is on the right, the other on the left of the 

 branchial sac in front of the greater portion of the alimentary 

 tube. The oviducts advance a short way beyond the ovaries, 

 and open into the cloaca, one on each side of the intestine, but 

 considerably in advance of the anal orifice. The testis is coin- 

 posed of numerous elongated, simple or lobed vesicles, which 

 are placed with one end in contact with the sides of the ovaries, 

 and are arranged in parallel order at right angles to them, 

 fringing both sides of these organs from end to end. From 

 the proximate extremities of the vesicles extremely delicate 

 ducts pass across the surface of the ovary, to which they are 

 attached, and go to join the vas deferent that extends along the 

 middle line from end to end of each ovigerous organ, and, 

 advancing along the oviduct, terminates at the extremity of 

 tli at tube. 



I have not met with this peculiar arrangement of the 

 genitalia in any other species, though, after all, it is but as it 

 were an amplification of that which we have seen to exist in 

 the compound genital masses in Sfijeln, title rosa and its imme- 



