ACADEMY OF SCIENCES. 156 
16. S. Intermedius, A. Ag. 
Two specimens in this collection appear to belong to this species, as they 
have the greenish spines and the small tubercles upon the anal system men- 
tioned in the description by A. Agassiz; the locality, however, is different, as 
that author gives Japan, while these are from the Sandwich Islands. 
Family ECHINIDA. 
In this family the ares of pores in the poriferous zone are never composed 
of more than three pairs. It is divided into two sub-families, the Temnopleu- 
ride, characterized by peculiar pits at the angles of the coronal plates, and 
the Triplechinide, which have short, straight ares of three pairs of pores. 
Sub-family TRIPLECHINIDZ. 
ECHINUS. 
17. E. Esculentus, Linn. Norway. English Channel. 
18. EH. Margaritaceus, Lamk. Patagonia. California. 
The specimen in this collection was dredged in 40 fathoms, at San Pedro, 
by W. J. Fisher. 
19. HE. Norvegicus. Norway. Mediterranean. Straits of Florida. . 
20. HE. Miliaris. Norway. English Channel. 
Genus TOXOPNEUSTES. 
21. T. Pileolus, Agassiz. Panama. Gulf of California. Viti Island. Mamnzi- 
tius. East India Islands. 
HIPPONG. 
22. H. depressa, A. Ag. Gulf of California. 
23. H. variegata, A. Ag. Sandwich Islands. Japan. East India Island. 
Viti Island. Red Sea, Mozambique. 
This species is smaller than H. depressa, from which it is easily distinguished 
by the small size of the tubercles, by the absence of tubercles in the inter- 
ambulacral and median ambulacral spaces between the ambitus and the 
abactinal pole, and by the coloring (usually violet) of those spaces. 
Sub-order CLYPEASTRIDZ. 
This sub-order, intermediate between the regular Echiniand the Petalostiche, 
contains Echinoids with very low, flat tests, petaloid ambulacra, and anal 
opening detached from the apical system, so as to give, as in the Petalostiche 
or Spatangoids, an anterior and posterior extremity. They differ from the 
Spatangoids in the possession of jaws, which are, however, much simpler 
than in the regular Echini, and articulate upon the auricles of the test, 
