CASTALIA PUNCTATA. 123 



lines (E. M.) ; between layers of shale near low water-mark at the East Rocks, St. 

 Andrews (R. M.) ; interstices of laminarian roots in Bressay Sound, Shetland ; Cumbrae 

 (Dr. Robertson). 



Extends to various parts of Norway, where it was first found by 0. F. Muller on 

 oyster shells. 



Head somewhat square, pale yellowish throughout with two closely approximated 

 dark red eyes on each side, the anterior pair obliquely elongated and wider apart, and 

 showing a cuticular lens anteriorly. From the anterior border two slender tentacles 

 arise, and external to each is a palpus having an enlarged basal segment with a more 

 slender conical distal region separated by a marked shoulder. Three pairs of tentacular 

 cirri follow, the dorsal cirrus of the third pair being the longest process in the body. 

 These cirri are very long, slender, slightly tapered organs, and arise from a prominent 

 ceratophore. 



Body about an inch in length, most massive anteriorly, and gradually diminishing 

 posteriorly where it terminates in two long cirri. The feet are least prominent anteriorly, 

 and gradually increase in length as the body diminishes, though posteriorly they again 

 become small. The ground-colour of the dorsum is dull yellowish crossed transversely 

 by dark belts (two in each anterior segment), which do not make a solid bar except in 

 the centre of the dorsum, the sides forming an elongated space in which the pale ground- 

 colour of the dorsum appears. Even the dense central portion of the bar is for the most 

 part crossed by fine pale lines. The dark pigment-belts become less and less complete 

 towards the posterior end, where they form only transverse touches. The posterior two- 

 thirds of the dorsum (behind the proboscis) has an olive-hue from the alimentary canal. 

 A dark speck occurs at the base of each foot, one at the base of the cirrus, and one 

 between the feet. These touches become more distinct posteriorly as the central pigment 

 wanes. The dorsal blood-vessel, which alters its course at the posterior end of the 

 proboscis, also enlivens the region. The grouping of the dark transverse belts on the 

 massive anterior region renders it one of the darkest parts of the body. The ventral 

 surface has a dull yellow or salmon-hue with a brown stripe, which increases in density 

 posteriorly, in the median line. The longitudinal pigment-striae are interrupted at the 

 segment-junctions so that the band is elaborate. The cirri are all pale and of extreme 

 tenuity. The proboscis in extrusion is a short barrel-shaped structure — with a broad 

 median notch ven tr ally — flanked by an elevated ridge showing prominences or papillae, 

 and having four prominent papillae along the dorsal arch. The whole organ is firm and 

 resilient, and the aperture is spacious. 



The intestinal canal is ciliated. 



The foot (Plate LXIX, fig. 14) is distinctly biramous, the dorsal spine piercing the 

 base of the dorsal cirrus. The latter springs from a peduncle (ceratophore) and is of 

 proportionally great length, diminishing, however, from before backward. The dorsal 

 bristles are slender, pale, tapering, and simple, ending in a smooth point (Plate LXXVIII, 

 fig. 2). The inferior lobe is largely developed, and has a median, a dorsal, and a ventral 

 papilla, so that the region appears to be trifid. The spine pierces the median papilla, and 

 the bristles form a broad fan, the ventral, however, being shorter than those above them. 

 The bristles are compound (Plate LXXVIII, fig. 2 a)., the shaft differing from that in 



