MALMGBEMA CASTANEA. 379 



in the ventral division of the other species, it is here a broad terminal flap or lobe with a 

 bluntly rounded margin in front of the tuft of bristles. 



The bristles are as translucent as in the former species, but are scarcely so long in 

 proportion. The dorsal are smaller than in 8, communis, and slightly curved, the 

 spinous rows being less prominent, and covering a much shorter region of the bristle 

 (Plate XL, figs. 20 and 21). About seven or eight are visible. The tip is bluntly 

 rounded, with a minute terminal claw and a small secondary process — with a notch 

 between. 



The ventral division has a fan-shaped series of slender bristles, which, as in the 

 former case, expand at the end of the shaft, where a small collar of spines occurs, the 

 finely spinous region, with a slight bend to the dorsal edge, tapering to the tip, which 

 turns bluntly round to the spiked side and ends in a small hook ; then follows an edge 

 directed obliquely backward between this and the secondary process, which is lateral 

 (Plate XL, fig. 22). So fine are the spines on the terminal region that they are scarcely 

 visible, but the oblique lines in lateral view are distinct. The whole bristle thus charac- 

 teristically differs from that of 8. communis. 



Habits. — This is evidently a commensalistic form on an Echinus, for Pedicellarige 

 frequently adhere to the skin and processes. 



"What relationship the Bermadion echini of Professor Giard l has to this species 

 remains to be seen. It is evidently a closely allied form, but the minute characters of the 

 bristles are not given with that distinctness which is necessary for critical diagnosis. 

 It is interesting in this respect, that 8. assimilis was found by Harvey-Gibson near Port 

 Erin, Isle of Man, coiled round the peristome of Echinus esculentus, protected by the 

 peristomial spines. This author gives some interesting structural details. Hornell also 

 (1891) found one on the spines of Echinus esculentus near Liverpool Bar. 



Genus XVIII. — Malmgeenia, Mcintosh, 1876. 



Head somewhat pyrif orm, with the narrow end in front, devoid of peaks, the median 

 and lateral tentacles springing from the front as in Lepidonotus. Eyes large, nearly 

 forming a square. Palpi, tentacles, and cirri smooth. Body of moderate length and 

 breadth. Segmental eminences fairly developed, but without papillae. Scales, fifteen 

 pairs, smooth with the exception of a small group of papillas at the anterior curve. 

 Dorsal bristles translucent, short, and with faint spinous rows. Ventral bristles trans- 

 lucent, with rather short distal regions and five rows of spines ; the tip hooked, and a 

 secondary process beneath. 



1. Malmgeenia castanea, Mcintosh, 1876. 



Specific Characters. — Head somewhat pyriform with the harrow end in front, 

 without peaks, the lateral and the median tentacles springing from the front as in 

 Lepidonotus. Eyes large, nearly forming a square ; anterior pair in front of lateral 



1 ' Bullet, so. Nord/ i, 1886, p. 8. 



