1894. PROCEEDINGS OF THE NATIONAL MUSEUM. 699 



for the retraction of the siphons; this is doubtless performed by the 

 contractility of the thick and wide muscular mantle edge. The mantle, 

 owing' to its thickness, affords abundant s^iace for blood sinuses, but 

 they are less marked than in Euciroa. The pericardium, proportion- 

 ally, is much smaller than in Euciroa. and the ventricle of the heart is 

 reduced to a small, rounded-triangular body, which is perforated by 

 the rectum, gives off an anterior aorta and two unequal lateral auricles, 

 either of which is as large or larger than the heart itself, and the right 

 auricle distinctly larger than the other. The position of the pericar- 

 dium with respect to the hinge is about the same in both genera. 

 Below and around it, occupying a very large part of the upper portion 

 of the visceral mass, is the ovary, easily discriminated from adjacent 

 structures by its deep purple color. This is due, not to the ovary itself, 

 apparently, but to the presence of the nephridiuni more or less closely 

 iuterramified with it. A section of the latter just behind the pericar- 

 dium shows that 'it occupies, not only nearly the whole space between 

 the dome of the mantle and the roof of the anal chamber, but extends 

 on each side downward, occupying the lateral walls as well as the roof, 

 and is then produced inward from the mantle as a thick, longitudinally 

 plicate, and variously recurved lamina, forming equally part of the Hoor 

 of the anal chamber (into which its free edges project) and of the roof 

 of the peri-pedal or branchial chamber. It thus contributes to form 

 about half the septum between the two chambers, and, unless the 

 fleshy septum of the typical Verticordia proves on reexamination to be 

 of this character, we have here an example of an unexpected and 

 wholly new element contributing to the building up of that part of the 

 organization. Investigation shows that an analogous but less conspic- 

 uous instance may be found in some species of LyonsieUa. 



Internally the nephridium is irregularly cavernous in its thicker parts, 

 traversed by multitudinous columnar fibers covered with a glandular 

 endothelium. Where the walls of the organ are close together as they 

 are laterally, and in the recurved lamina, the fibers run almost directly 

 from one wall to the other. In the thicker portion they pass radially 

 in every direction. The substance of the ovarian gland is whitish, and 

 from its surface project in various stages of protrusion and peduncula- 

 tion the growing ova, which are externally smooth and opaque, but in 

 the free ripe ova are covered with a thin, perfectly transparent layer. 

 The nephridia, or organs of Bojanus, carpet much of the peripheral 

 and part of the internal surfiice with a rich deep purple glandular 

 tissue, giving rise to multitudes of circular, somewhat compressed, cal- 

 careous granules, which, by transmitted light, appear of a rich amber 

 color with a strongly marked nucleus. The ova are discharged in large 

 numbers into the anal chamber, where they lie immersed in a trans- 

 parent glairy mucus, which does not seem to be affected by water. I was 

 unable to find any eggs which showed signs of segmentation. The walls 

 of the laminar portion of the nephridia are double, externally smooth, 



