WOODWARD : EPHIPPODONTA. 23 



portion of the visceral mass. So that we now find four sub-divisions 

 of the supra-branchial chamber. The two innermost ones communi- 

 cate with the branchial chamber by a slit situated between the gill 

 and the posterior portion of the visceral mass (Figs. 12 to 15, sp.h.c.) 



The Foot is very large, and Tate describes it as " somewhat disc- 

 shaped " in the contracted state ; ^ however, this is not apparent in 

 my specimens, the most striking feature being its sub-di\dsion into 

 three lobes visible both from below and from the side, the anterior or 

 free portion being roughly pointed and tongue-shaped. The two 

 posterior lobes which are more closely united to the body contain the 

 byssal gland; viewed from below (Fig. 1,5.) they present an elongated 

 groove which widens out in the posterior lobe, and from which the 

 byssus protrudes. Tate makes no mention of this byssal groove, 

 although it is a most conspicuous feature. The byssal gland is well 

 developed and situated in the middle lobe of the foot ; the groove, 

 which extends for some depth into the foot and giving off a few 

 irregular diverticula, suddenly divides into two, the two halves 

 curving gracefully outwards and receiving a dorsal series of curved 

 ducts, so that one might roughly compare it with a palm-tree (Figs. 3 

 and 10, b.g.). Both Galeomma and Scintilla are byssiferous. 



The Respiratory and Circulatory systems: — The gills oi Ephippodonta 

 are those of a typical Eulammellibra,nch, and consist of two pairs of 

 lamellae ; the internal ones extending slightly in front of the external 

 ones (Figs. 4 and 5, g^ and g-), which latter overlap the former behind 

 and fuse with one another in the middle line in this region. In 

 the contracted state (Figs. ] 1 and 12) each lamella is bent so that its 

 free edge forms an angle with the main portion, the flexure tending 

 towards the median line. 



The histology of the gill filaments is not easy to make out, as the 

 latter are veiy much caked together, but it does not appear to differ 

 in any way from that of the more typical forms (Fig. 17). 



The heart is small and difficult to make out ; it consists of a pair of 

 auricles and a small muscular ventricle, the latter being perforated by 

 the rectum (Fig. 12, v.au.). The fiirther details of the blood vessels 

 and other circulatory organs I have been unable to determine with any 

 precision. The pericardium (.^;.) is large and surrounds the heart and 

 rectum. The kidneys (Fig. 13, h.) are situated just dorsal to the 

 visceral (olfactory ? or parieto-splanchnic) ganglia, and appear to be 

 perforated by the posterior pedal retractors. They consist of well 

 marked coiled tubular, glandular segments, and large receptive 

 bladders which communicate with one another across the middle line 

 and with the supra -branchial chamber on either side of the body close 

 to the opening of the genital ducts ; the reno-pericardial aperture I 

 have not seen. 



The Oenital Glands. — The sexes are distinct, but I have only examined 

 males, as all four of my specimens belonged to that sex. The testes 

 are diffuse, tubular glands extending forwards as far as the stomach, 

 and ramnifying amongst the intestines and liver and back to the kidneys 



' In his second paper Tate corrects this error. 



