ASOIDIA MAMILLATA. 73 



narrow, strongly pectinated or transversely 

 ribbed. Br<uir]/in/ tn/>rn-le. inconspicuous.] 

 Leiiijtlt from three to four or five inches. 

 Ha/>. Adhering- to loose stones, etc. 



ENGLAND. Not uncommon on the south coast ; rare 

 or entirely absent in the north. Luhvorth Cove 

 (Jeffreys) and We y mouth (trow), Dorset. Salcombe 

 Bay (Hinclcs), Tor Bay (Aider), and Plymouth 

 (Stewart), Devon. [Falmouth, Cornwall (Cocks, I84Q).] 

 Isle of Man, rare (Alder). 



SCOTLAND. Lamlash Bay, Arran, rare (Alder). 



First record. Forbes, 1848, as A. arachnoidea. 



This species (PL I) adheres diagonally by the base, 

 from which it often throws out ramifications of the 

 test to a considerable distance, running among loose 

 stones and binding them together into a compact mass. 

 On account of the bend of the mantle and branchial 

 sac upwards, the anal aperture is displaced from its 

 usual ventral position, and appears generally on the 

 left side, sometimes even assuming a sub-dorsal aspect. 



The bending of the body upwards is a very striking 

 feature in the species, and does not merely alter the 

 situation of the excurrent tube as stated above, but 

 throws many of the organs out of their regular position. 

 The bend is to the right side, inclining towards the 

 ventral margin, and the lower extremity of the mantle 

 is brought nearly as far forward as the anterior border 



t> 



of the intestinal loops. The branchial sac, which 

 extends to the lower end of the body, is also bent 

 upwards, and consequently the endostyle forms a 

 very wide loop ; the heart is likewise bent in the 

 same direction, and the upper portion of the 

 endostyle is drawn somewhat towards the ventral 



ts 



margin. In fact, while the dorsal margin is in a 

 manner much elongated, the ventral margin is greatly 

 shortened, so that the oral band can be little more 

 than one third the length of the endostyle. The band 

 itself is narrow and strongly pectinated or ribbed 

 transversely, and is in front split into two lateral mem- 



