188 SPATANGACE^E. 



post-anal impression of the former, and a dorsal impression 

 peculiar to itself. One British species, which I have called 

 the Fiddle Heart-Urchin, on account of the peculiar shape 

 of the dorsal impression, belongs to it. The Brissus lyrifer 

 I cannot find described or figured in any author on this 

 subject. It is a very handsome and remarkable species, 

 having a red body, with pale yellowish white spines, and 

 the dorsal and post-anal impressions of a rich brownish 

 purple. It inhabits mud at the depth of from ten to 

 fifteen fathoms in various localities in the estuary of the 

 Clyde, as off the island of Cumbray, in Rothsay Bay, and 

 the Kyles of Bute, in which places I met with it for the 

 first time in July 1840. I have a specimen one inch and 

 three-fourths in length by one and three-tenths in breadth, 

 and one inch in height. I found fragments which indicated 

 that it attained larger dimensions. 



In form it somewhat resembles a slightly depressed egg ; 

 the back is convex and highest posteriorly. It is thickly 

 clothed by long curved spines, those within the post-anal 

 impression forming two caudiform tufts, and on the post- 

 oral space they are long, slender, and spathulate at their 

 extremities. On the back the four lateral ambulacra are 

 placed in depressions, and form a St. Andrew's cross. 

 Each of them is included within the dorsal impression. 

 The ovarian holes are placed in the centre at the origin 

 of the four ambulacra ; two of them are placed close to- 

 gether, and the two anterior diverge. The ambulacra are 

 ovate, petaloid in form, and have the holes so placed that 

 the four rows composing the two sets of pairs, are al- 

 most equally distant from each other, The two anterior 

 ambulacra are longer than the two posterior, and the 

 numbers of pairs of suckers in each of the two anterior 

 are eighteen and twelve, and in each of the two posterior 



