from the Island of Malta. 67 
ambulacral areas. The jaws are absent in all the specimens we 
have examined. The anus is a small round aperture, situated 
near the posterior margin of the base of the test; in some 
specimens it is elongated in the transverse diameter, and 
measures about ,%ths of an inch across. The tubercles are 
nearly of the same size on the upper surface, and their summits 
are level with the test, so that the areolas which surround them 
are excavated out of the superficial layer of the calcareous plates. 
The intertubercular surface is ornamented with a microscopic 
granulation, disposed in circles around the areolas of the tu- 
bercles, and filling up all the intervening spaces. The tubercles 
at the base are larger and more closely set together than those 
on the dorsal surface; a row of five or six tubercles is seen on 
each of the interfissural bands of the poriferous avenues. 
Affinities and differences.—C. altus has many traits in common 
with C. rosaceus. In the general outline, in the size, form and 
extent of the ambulacral areas, there is much resemblance ; but 
the campanulate form of the dorsal surface, the smallness of the 
apical disc, and the truncature of the posterior border constitute 
differences which may be traced through all the varieties 
C. altus assumes. The thickness of the marginal fold, and the 
great development of the ambulacral flower, when compared 
with the thinness of the border and the limited extent of the 
ambulacra, distinguish at a glance C. altus from C. Tarbellianus, 
C. marginatus, and C. scutellatus. The dome-shaped upper 
surface of C. umbrella, with its flattened ambulacral areas and 
convex prominent interambulacral spaces, its star-like apical 
dise and small mouth-opening, widely distinguish this species 
from C. altus. The affinity, however, is very near between 
C. altus and C. crassicostatus, the principal difference consisting 
in the more prominent rib-like prominence of the ambulacral 
areas. 
Stratigraphical position.—This is the most abundant of all 
the Maltese Urchins. It is collected from bed No. 2, the 
yellow sand, associated with C. Tarbellianus, Echinolampas 
Richardi, and the other Echinoderms enumerated in the palzon- 
tological résumé given in the introduction to this memoir. The 
test is very well preserved in most specimens. Those from the 
sand with black particles are in the finest preservation. In this 
stratum the Urchins are accompanied with Terebratula ampulla, 
Pecten squamulosus, P. Burdigalensis, Ostrea Virleti, O. navicularis, 
and masses of Lenticulites complanatus, with Cellepora mammil- 
lata, Escharina monilifera, and other Bryozoa. 
It has been collected from the Miocene beds of Port-de-Bouc, 
Saint-Miniato, Tuscany; Nice, Turin, Ile de Créte, Ile de 
Caprée ; Bonifacio, Corsica; Oran. The Maltese specimens are 
