143 



These echini differ from those of the preceding genus by 

 their extended ambulacra ; they are also larger, and of a 

 more oblong form. 



Sp. 1. Echinoneus cyclostomus. Ovato-oblong, rather 

 depressed ; though pulvinated ; five pores in the vertex ; 

 the mouth round. Recent. Leske ap. Klein, Tab. xxxvii. 

 fig- 3, 4. 



2. E. semilunaris. Ovato-oblong, rather depressed ; with 

 four pores in the vertex ; the mouth oblong, obliquely 

 transverse. Recent. 



Echinon. minor de semilunari. Leske ap. Klein, Tab 

 xlix. fig. 8, 9. 



3. E. gibbosus. Ovate, turgid, irregular ; vertex excen- 

 trical ; ambulacra waved ; the mouth oval, acute, and ob- 

 liquely transverse. Recent. 



One species remains which is placed under this genus, 

 but not without some hesitation. It is figured, by Scilla, 

 Tab. xi. fig. 1, 2, and is named, by Phelsum, echinoneus sou- 

 tiformis ; but its characters are such as to render it difficult 

 to determine under what genus it should be placed. 



It is placentiform, its circumference oval ; the ambulacra 

 striated, passing from the vertex nearly to the mouth, where 

 they terminate in slightly depressed grooves ; the mouth is 

 in the middle of the base, obtusely pentagonal ; the vent 

 towards the margin. 



The striated rays, with the grooves in the base, agree 

 with clypeus ; the structure and disposition of its ambulacra 

 with clypeaster ; whilst its outline and form, with the position 

 of the mouth and vent, approximate it to scutella. 



No figure of this genus is given, since, to obtain an idea 

 of its appearance, it is only necessary to connect its ovoidal 

 boat-like form with the situation of the mouth and vent, as 

 in the preceding genus, the ambulacra being continued 

 from the vertex to the base. 



