55 
he Echinodcrmata oj Jlew Brunswick. 
Order III. SPATANGIDEA (Heaht-Urchiks). 
Irre<jalov Eckinoids more or less heart-shaped, with eccentric mouth, no teeth, and 
usually a four-leaved ambularral rosette. 
FAMILY SrATANfilL.L. 
21. Schizaster fragilis, (Dukej^ akd Koren), Agassiz. 
One of the “Heart-Urchins.’’ 
Descriptiox. (0) p. 368. 
Figure. (0) pi. XXL 
Distributiox. {a) General;— ^0 to 321 fathoms. Straits 
of Florida, Bay of Fiindy, Gulf of St. Lawrence, Lofoten 
Islands, Norway. 
(b) In N. B. waters ; — Centre of the Bay of Fundy, east of 
Grand Manan, 95 to 106 fathoms, Verrill, (R). Deep parts 
of Gulf of St. Lawrence, “widely distributed in the deep-sea 
mud,” Whit eaves, (P). 
This fine Sea-Urchin is a member of the Syrtensian and not of the 
Acadian Fauna, and is hence not likely to come into the hands of many 
of our collectors. It is the highest in organization of our Echinoids, a 
fact which impresses the observer at a first glance, for the radial sym. 
metry is disguised so that its bilateral symmetry, showing a differenti- 
ation from the typical radiate towards a higher type, first strikes the 
eye. 
In outline it is round heart-shaped, a little more than half as high as 
long. Large specimens are two and one-half inches in length, but the 
average is rather smaller. It is covered with short (one-eighth to one- 
fourth of an inch), slender brownish spines, which are largest about the 
branchial rosette. The latter is not regular as in the Cake-Urchin, the 
three anterior petals being much larger than the others. Running 
around the rosette and close to the tips of the petals is a line, the fasci- 
cle, which bears, not spines, but minute ciliated bristles. The mouth 
is not placed in the centre on the under side as in our other two forms, 
but near one end, where the shell forms a prominent lip to protect it. 
Owing to its eccentric position the ambulacra! grooves radiating from 
it are of unequal lengths. 
It lives chiefly upon muddy bottoms, but nothing further is known 
of its habits. There is some uncertainty about its development, but it 
is believed to pass through a metamorphosis somewhat similar to that 
•of Strongyloceutrotus, with a free-swimming larva or Pluteus. 
