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 f 

 C. marginatuSy 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 

 disc 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 palseon- 

 tological resume 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- 

 lattty Escharina monilifera, and other Bryozoa. 



It has been collected from the Miocene beds of Port-de-Bouc, 

 Saint-Miniato, Tuscany; Nice, Turin, He de Crete, He de 

 Capree; Bonifacio, Corsica; Oran. The Maltese specimens are 



