B1UTISH TUXICATA. 



the dorsal and ventral margins, over the alimentary 

 canal, and at the margin of the orifices. In one speci- 

 men a broad belt of brilliant crimson extended along 

 the dorsal margin, commencing in the branchial tube 

 and reaching to the bottom of the mantle. The anal 

 tube in this specimen was also of a deep crimson. 

 The branchial aperture is sub-terminal, being placed a 

 little towards either the left or right side ; in one of 

 the specimens it was inclined to the right, in the other 

 two to the left side. The anal tube, which is a little 

 more than half-way down the side, is well produced, 

 but is somewhat constricted and turned over towards 

 the left side. 



The branchial sac (PL XVII, fig. 4) does not extend 

 backwards beyond the visceral mass; it is minutely 

 plicated ; the primary vessels are numerous and regu- 

 larly disposed, and are placed closer together than 

 usual. The branchial ties are large, with very stout 

 walls. The secondary vessels are short and wide 

 -the stomata being extremely short, wide, and ellip- 

 tical many of them not extending the whole space 

 between the primary vessels. The longitudinal bars 

 are stout, with the branchial papilla? rather closely 

 set; the larger ones, at the intersections of the meshes, 

 are rather short and thick with the extremities obtuse ; 

 those placed between them are considerably smaller, 

 and are somewhat clavate, their extremities being a 

 little enlarged and rounded. The papillary membrane 

 is ample. The oral lamina (PL XIX, fig. 3) is not very 

 wide ; the anterior cleft extends further down than 

 usual and is delicately ribbed transversely, the ribs 

 being scarcely visible on the left side ; the margin is 

 minutely denticulated. In front of the mouth the la- 

 mina dies out, and is replaced for some short distance by 

 ;i series of delicate tentacular points ; below the mouth 

 the lamina is verv narrow and indistinctly ribbed and 



tj ' 



pectinated. The tentacular points on the left side of 

 the mouth are narrow and minute, and arranged in a 

 closely set series ; they diminish in size backwards 



