138 



2. C. altus. Subovate ; vertex conoidal, considerably 

 vaulted ; areas granulated, the larger without, the smaller 

 within, the petaloidal spaces formed by the ambulacra. 



This species is only known in a petrified state. It is 

 distinguishable by its size, being, sometimes, six inches 

 long, and two inches in height, by its rising in a round 

 vaulted form ; and by its ambulacra being large and wide. 

 Fossil. 



The casts of the two last species form very interesting 

 fossils. Organic Remains, PL ii. fig. 8, and PL iv. fig. 7. 



3. C. ovatus. Ovate ; the margin not waving, the upper 

 part convex, with four pores in the vertex ; the ambulacra, 

 in petaloidal forms, not united at their lower terminations, 

 but the one side of each ray extending farther than the 

 other ; the surface covered with minute tubercles ; the base 

 flat ; the mouth subreniform, with five prominent lips, from 

 the hollowed spaces between which proceed five grooves ; 

 the vent in the margin. Recent and fossil, Leske ap. 

 Klein. Tab. xx. fig. c. d. 



4. C. orbiculatus. This is a fossil which was placed, 

 by Leske, under this genus, with considerable doubt, it 

 being so injured that the state of the under part could not 

 be ascertained. 



5. C. marginatus. With a convex stelliferous vertex ; 

 with short ovato-acute ambulacra ; the margin rather thin, 

 expanded, and broad. Fossil. Scilla, Corp. mar. Tab. xi. 

 fig. inferior. 



6. C. scutiformis. Elliptical ; the back flattish and sub- 

 marginated. Seba, mus. iii. Tab. xiii. fig. 23, 24. Encyc. 

 PL cxlvi. fig. 1, 2. 



7. C. laganum. 



Echinodiscus laganum. Leske ap. Klein, Tab. xxii. 

 fig. a. b. c. 



8. C. excentricus. Suborbicular, depressed, but rather 

 convex ; five narrow ambulacral compartments divaricating 



