ACADEMY OF SCIENCES. 153 
ARBACTA. 
3. A. stellata, Gray. Gulf of California. Panama. 
Family DIADEMATIDZ. 
Test thin, ambulacra narrow. Spines long, hollow, verticillate or trans- 
versely striated; tubercles of ambulacral and interambulacral areas similar. 
Auricles not forming connected arcs. Pores in arcs composed of three pairs. 
DIADEMA. 
4. D. Mexicanum. Acapulco. Cape St. Lucas. 
5. D. setosum, Gray. Cape Verde Islands. Japan. Sandwich Islands. 
Feejee Islands. 
A single specimen from the Bonin Islands, presented by W. J. Fisher. 
ECHINOTHRIX. 
6. £. calemaris, A. Agassiz. East India Islands. Society Islands. Phil- 
ippines. 
A single fine specimen, presented by W. J. Fisher, naturalist of the ‘‘ Tus- 
carora,’’ and dredged from a depth of ten fathoms, off the Bonin Islands. 
When first brought in, there was observable a singular swelling at the apex, 
which led me to suspect there might be a parasitic crustacean within; a sup- 
position which was afterwards verified by the extraction of a fine specimen 
of a new species of the family Pinnotheride, measuring fully 14% in. across 
the legs. The family Pinnotheride are all parasitic, inhabiting the mantle of 
oysters, mussels, Haliotis, and other mollusks, and also, as in this instance, 
the extremity of the digestive canal of certain Echini. 
Family ECHINOMETRADZ. 
This family contains many genera and species, all of them distinguished 
from the Echinide proper by having the pores arranged in arcs of more than 
three pairs. In many cases, the outline is a long oval, and the axis is oblique, 
that is, it does not coincide with the center of either ambulacral or inter- 
ambulacral areas. 
HETEROCENTROTAS. 
7. H.mammillatus, Brandt. Zanzibar. Red Sea. East India Islands. 
Sandwich Islands. Feejee Islands. Gulf of California. 
Alexander Agassiz, in his ‘‘ Revision of the Echini,’’ gives all these locali- 
ties except the last; but we have in our collection unmistakable specimens of 
this fine species, brought to Prof. George Davidson from Cape St. Lucas. 
The spines of H. mammiilatus are very large, and vary in shape from that 
of a cricket-bat to that of a bayonet; and the test is very strong and thick. 
Proc. Can. AcAD. Scr., Vou. VI.—11. 
