ACADEMY OF SCIENCES. L57 
ECHINARACHNIUS. 
28. E. eacentricus, Val. 
This is the common cake-urchin of the Pacific coast, found at all points 
from Sitka to Monterey, and also at Kamtschatka. It is extremely common 
at the mouth of San Francisco Bay, where it lives in great numbers on the 
bar, on a bottom of sand and a little mud, at a depth of from five to seven 
fathoms. The district inhabited by it extends for a length of four or five 
miles, and the width of a mile along the west and southwest part of the bar. 
29. E. mirabilis, A. Ag. 
This author gives Japan as the habitat of this species; but it is also found 
in Alaska, as we have two fine specimens from the Shumagin Islands, pre- 
sented by W. H. Dall. 
30. E. parma, Gray. 
A. Agassiz gives New Jersey, Labrador, Vancouver Island, Kamtschatka, 
and Australia as habitats of this species. Our collection contains some 
specimens from Hakodadi, Japan, presented by W. J. Fisher. 
MELLITA, 
31. WM. longifissa, Mich. Panama. Gulf of California. 
ENOOPE. 
32. . Californica, Verrill. Panama. Mazatlan. Gulf of California. 
One of our specimens is curiously deformed anteriorly and posteriorly, so 
that its transverse diameter greatly exceeds its longitudinal diameter. The 
abactinal side is jet-black, with a velvety surface of small spines; but the 
actinal side, where the spines are comparatively large, is of a mouse tint. 
33. E. grandis. Gulf of California. 
Of this massive species we have one fine specimen, presented by W. G. W. 
Harford. 
Sub-order PETALOSTICHA. 
These Echini have no teeth; the anal system is separate from the apical; 
the ambulacra are petaloid; the test is less flat than in the Clypeastroids; 
certain parts of the test and spines are greatly specialized; and the radiate 
form is accompanied with an evident bi-laterality. 
Family CASSIDULIDZ. 
Petalosticha without plastrons or fascioles, on which the spines are arranged 
differently to the rest of the test. They approach the Clypeastroids in many 
respects, but have no teeth, and in form simulate the regular Echini. 
